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placed a weight which is made to close the valve again as the cam revolves. The diameter of the fly-wheel is 20ft. 6in., and the size of the rim is 16in. by 7in. The crank shaft journals are each 1ft. 5in. long, by lft. diameter; the length of the crank is 5ft. 4 in., and the length of the sweep röd is 27ft. 8in. The blowing cylinders are each 100in. in diameter and 8ft. 6in. stroke; the valves are made with leather and a plate of sheet iron at the back; the piston is constructed with angle irons and two collars of leather turned up in the usual way. The distance between the centres of the cylinders is 26ft. Sin., and the length of the beam between centres is 30ft. lin. The tuyere pump is of the bucket-and-plunger variety, with a plunger 9in. diameter. From the centre of the beam to the floor line the distance is 21ft. 8in.; the depth of the beam in the centre is 5ft. and at the ends 2ft. The pressure of steam at which the engines are worked is usually about 30lb. to the square inch.

OSCILLATING OR VARIABLE ECCENTRIC MOTION.

TH

The

HE term eccentric is applied in general to all such curves as are composed of points situated at unequal distances from a central point or axis. The ellipse (the curve called the heart, which is much used in the traverse motion of spinning frames, and even the circle itself, when supposed to be fixed upon an axis which does not pass through its centre), are examples of its eccentric curves. object of such curves, that are of frequent occurrence in machinery, is to convert a rotary into a reciprocating, rectilinear motion. The cam known among engineers and machinists as an eccentric, is a plate or pulley, turning on a shaft out of its centre. When keyed upon a shaft, we speak of the two centres as the centre formation and the centre of revolution by means of a surrounding strap, to which is attached a rod, we get the reciprocating rectilinear motion to the valves of steam engines; the same motion is common to pumps, feed gear of lathes, &c., and familiar to engineers and machinists who know that the degree of eccentricity or extent of throw given by an eccentric is equal to twice the distance between its centres of formation and revolution. The annexed engraving, for which with this description we are indebted to the American "Journal of Mining,"

represents an eccentric, with a great improvement, patented by Timothy Keeler and Geo. S. Avery, of Danbury, Conn., by which oscillation is obtained. The eccentric or cam is usually keyed rigidly upon a shaft, and the eccentric strap is fitted to work easily upon it; the rod, known as the eccentric rod, is attached to this strap, and gets a steady reciprocating rectilinear motion; but on reference to the accompanying engravings, figs. 1 and 2, it will be seen that by the attachment of the exterior band, F, the eccentric rod has perfect freedom to swing, while

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the eccentric cam, A, is keyed firmly to the shaft, and revolves in its true line of motion. Also, by this arrangement, the eccentric rod may be set, if required, at almost any angle to the line of eccentric motion, and still work freely. By this means, marble, wood, &c., may be sawed or cut, of a tapering or angular form, without changing or moving the body being cut; or angular or irregular grooves in iron, &c., may be cut or planed with facility. Also, by this arrangement, two or more eccentric rods, B, may be

attached to the same eccentric, for driving pumps or independent lathes. Offsets in eccentric rods can be frequently dispensed with, and the improvement is applicable and useful for feed motions, and in many cases which engineers will not be slow to discover.

THE DETERIORATION OF MARINE

BOILERS.

THERE are certain facts in boiler engineering, which yet remaining to be explained by satisfactory hypotheses, deserve to rank as mysteries. Among these we may cite two which are sufficiently remarkable. One is the exceedingly, and in some cases alarmingly, rapid deterioration of marine boilers by corrosion; the other is the failure by "coming down" of the crown plates of furnaces. The first presents itself not unfrequently under conditions and in a way which renders it absolutely inexplicable by any sensible theory. Attacking one side of the steam space, the other remains untouched. In boilers similar in every respect, corrosion takes place in one on the right side, in another in the left. Now it is the portion nearest the funnel which suffers most; again it is a single plate furthest from the uptake that is eaten away. The diseasefor such we may term it-appears under different forms. At one time the plates attacked are deeply pitted, at another the iron exfoliates in flakes. Mr. Bourne attributes steam-space corrosion to the action of superheated steam. We confess that to us the theory appears untenable. No marked difference can exist in the temperatures present in various portions of the boiler; and unless it can be proved that superheated steam is present in one place and not in another, it is difficult to see why one plate should suffer more than another. It is true that superheated steam much hotter than 280deg. disentegrates cast iron; but it has yet to be demonstrated that any corrosive effect of a similar character, or indeed of any kind, is exercised on wrought iron. The most probable solution of the problem is found in the effect produced by pure distilled water on wrought iron. It is now perfectly well known that distilled water from surface condensers rapidly destroys the plates of boilers, and in order to protect them it is necessary that sufficient salt water be admitted from time to time to maintain a thin coat of scale. If it can be demonstrated that pure water is brought into contact with the plates of a steam chest we can at once establish a reasonable

theory to account for their corrosion, as like causes usually produce like effects. Now, marine boilers are alternately hard worked and left at rest when the fires are drawn; as the boiler cools down pure distilled water will be precipitated on the steam chest plates by the condensation of the steam, and the water may be present in sufficient quantity, and the precipitating process may be sufficiently often repeated to render the corrosion with which we are dealing explicable. We do not assert that this theory and it is no more-is perfectly satisfactory, but we believe it to be the best yet broached.

quietly in dock, with not half the pressure in the
boilers which they had carried with ease before, and
with fires nearly out. It has yet to be shown that
pumping in cold water under such conditions of
heat and pressure can produce a collapse. The
whole story-for the truth of which we can vouch-
is highly instructive and interesting. The case is
nearly without an exact parallel, so far as we are
aware; and for the present we prefer that our
readers should draw their own conclusions. It is
quite possible that some among the number can cite
cases tending to throw a light on what at present
is an exceedingly curious episode in the history of
marino boiler engineering." The Engineer."

has, however, to be toughened, for which there is an extra charge. The private assayers of California, before the establishment of a Government Assay Office there, used to make no charge for the assay, taking their pay out of the drippings from the crucibles. The Government assayers account for the entire weight of the deposit.

A still more vexatious, and in many cases not less mysterious, kind of injury is the second we have named in the first lines of this article. Furnace crowns come down not unfrequently while there is plenty of water to all appearance in a boiler; while, in a word, no reasons within mortal ken exist for THE UNITED STATES ASSAY OFFICE IN might have been effected if it was first ascertained

their failure. We remember one instance in which the crowns of the furnaces in a large steamer, obstinately refused to keep their proper form, After many repairs the attempt to keep them right was given up in disgust, and the boilers were worked until they were worn out with the furnace crowns all more or less out of shape. After they had come down to a certain point they got no worse, and gave no trouble. In this case the circulation was bad, and the sinking of the furnace crowns appeared to improve it by giving more space over them. The boilers were defective in design, and the failure appeared to be, as physicians say of certain disorders of the human system, an effort of nature.

NEW YORK.

a

DJOINING the sub-treasury in Wall-street is granite building of modest appearance, bearing over its entrance the words "Assay Office." It is fitted up in the same style as a broker's office, and three or four clerks appear to be quite able to transact all the business pertaining to this Bureau without over exerting themselves. In fact, it would not appear at a first glance that much business is ever transacted there; yet there from 14,000,000 to 15,000,000 dollars of the precious metals are received and accounted for during the year. The larger portion of this is in the form of gold dust from California, Nevada, Montana, and Idaho. Much the larger portion of all the bullion received is either in the form of dust, grains, bars, or amalgam. A comparatively small quantity comes in the shape of gold and silver plate, watch cases, foreign coin, and ornaments. These are sent in by jewellers or private parties to be re-melted, for plate, watch cases, and ornaments change their fashion like other things of less value, and have to be remodelled to be saleable.

The depositor having received the full value of his deposit, the latter of course becomes the property of the Government, and it now has to undergo a process called "parting "before it is sent to the Mint, or used in any way for commercial purposes. In parting gold, silver is added in the proportion of about two parts in weight of silver to one of gold. Formerly no account was taken of the silver already in the gold, but Mr. Mason, in charge of the melting and refining department, found that a great saving how much silver the gold bullion already contained. This practice is now carried out, and instead of invariably adding two parts of to ver to the of good, only sufficient silver is added to make the proportions above stated. There is thus a saving, by Mr. Mason's method, of about 30 per cent in the material, and in one year the sum of 22,000 dollars was saved. The mixture of gold and silver is next melted, thoroughly mixed, and poured into water, by which it is granulated. The granules are placed in porcelain jars containing nitric acid. Heat is then applied, and as the acid boils, the yellow fumes which our readers have doubtless so often seen proceeding from the chimney of the Assay Office, are given off. This process goes on for about twenty-four hours, when the jars are emptied, and in the bottom is found a brown substance resembling mud or anything else upon earth rather than "gold-glittering gold." It is, in fact, however, pure gold, or at least, very nearly so. The silver has been dissolved by the nitric acid, and is in solution. It is carefully put aside for future treatment, for in the Assay Office nothing must be lost or wasted. The brown substance found at the bottom of the jars is placed in large wooden tubs and washed by percolation in warm water until all traces of acid have disappeared, and it is said to be "sweet."

But even in boilers carefully worked and of good design furnace crowns sometimes sink without previous warning under the most unaccountable circumstances. Within the last few weeks a case in point came under our notice which presents many points of interest. A new steamer, plying between Liverpool and Dublin, was fitted up with two boilers, one tubular of the ordinary construction, the other a flue boiler on a novel principle. The two boilers were introduced into the same boat in order to test the relative efficiency of the old and the new Few persons are aware of the actual quantity of systems. During the first month the ship was on gold produced by our mines since their first disher station she did, as is often the case undercovery. In a recent official report this amount is similar circumstances, a good deal of racing with placed, in round numbers, at 1,000,000,000 dollars. The gold is then of 940 fineness. Formerly it was older boats, in which she always won. Hard firing Since 1849, California has produced 900,000,000 subjected to a second boiling in nitric acid, which of course was not unknown on board her, and after dollars. Her productive powers, however, for the left it about 993 fineness, but by the process at a couple of weeks one furnace crown came down very last thirteen years have steadily decreased, and for present in vogue it is treated with sulphuric acid, by slightly in the tubular boiler, the other boiler remain 1869 the estimate is only 25,000,000 dollars. Mon- which a fineness of 998 is attained. This is termed ing all right. Hardly a month since the ship-we tana has produced 65,000,000 dollars; Idaho, pure gold although it is not actually so, but to dedo not at present feel ourselves at liberty to mention 45,000,000 dollars; Colorado, 25,000,000 dollars. prive it of the two parts of alloy it now contains names-came into Liverpool and hauled alongside The estimated production of Nevada in 1869 is would involve an expenditure of time, money, and the wharf. At this time her firedoors were open, placed at 20,000,000 dollars; of Montana, 12,000,000 trouble altogether useless. After its treatment with the fires very low, the safety valves blowing freely, dollars. It is believed that not more than 50,000 sulphuric acid, the gold, which still looks more like and not 101b. steam in the boiler, the regular pres- persons are now engaged in mining in this country-red mud than a precious metal, is again washed until sure being 201b. per square inch. The engineer a considerable falling off from the numbers of gave orders that some water should be blown out, previous years. and the boiler pumped up with the donkey engine. He then went on deck, and had not been there ten minutes when he was called down to the stokehole, as something was wrong. On looking into the four furnaces of the flue boiler he found that the crown plates of all had come down to an extent very little short of absolute collapse; not twenty minutes before they were all right under 201b. steam.

Our readers will, we think, join with us in saying that in this case there is much that is sufficiently re markable. There was no reason to think, from the previous performance of the boiler in question, that the circulation was deficient in any respect; and it is next to certain that it must have been sufficient with low fires and blowing safety valves if it sufficed for hard firing and high pressures. Was there time under the conditions for the furnace crowns to become red-hot, even though the circulation was bad? We think not. One explanation assigned was that all the water, or nearly all, had been blown out, and that the introduction of cold water brought about the catastrophe. This theory is not supported by good evidence; the stoker in charge asserted that the water was not blown low enough to strip the furnace crowns, and, indeed, these lie so low that had they been bared the boiler must have been nearly emptied. Again, if the water had been blown too low, would not the flue crowns, especially at the back of the boiler, being much longer exposed than the furnace crowns, have manifested some signs of overheating? We think so; but no trace of injury was to be found on them. Under the circumstances, we are driven to conclude that the pumping in of cold water does not suffice to account for the injury. According to this theory it is assumed that the furnace crowns were laid bare by priming while at sea, and that they then came down, but that the injury was not discovered till long afterwards, when the introduction of cold water made the seams leak. In considering this explanawe have to bear in mind that the furnace crown, on which the cold fluid impinged most directly, should saffer most, but, so far as we can learn, no such effect was produced, nor has it been proved that any considerable quantity of cold water was ever pumped in. Nor is it likely that the crowns could have come down on the trip without discovery. The entire subject is fraught with mystery. Here we have a boiler which works satisfactorily for weeks, carrying 201b. steam, and when hard fired giving out without a moment's notice, when lying

The deposits received having been carefully weighed and a certificate given, are numbered and sent at once to the melting room, a spacious apart ment provided with furnaces, tanks, &c., and floored with iron tiles. Each deposit, or as much of it as can be conveniently handled at once, is placed in a crucible, and, as soon as melted, is poured into iron moulds. If the deposit is of gold, two pieces are cut from the lump and set aside for the assayer. If of silver, a small portion of the fluid metal is dropped into water, which granulates it, and these granules are used by the assayer. The crucibles are carefully scraped after being used, so that not a particle of the metal is lost, for the assayer, it must be understood, has to account for every grain of the metal received.

sweet." It has now a reddish yellow hue. After being dried, it is taken to a hydraulic press, where it is made into "cheeses," so called from the colour and shape. The cheese made in the Assay Office is richer far than the most fertile vales of Gloucester ever produced. Each "cheese" is but 13in. in diameter, but it is worth about 20,000 dollars. These cheeses are baked in an oven heated by steam until all

remaining moisture is expelled, when they are remelted, cast into bars or bricks, assayed and stamped with the weight, fineness, and value. And now they look like gold indeed.

The reader will remember that nitric acid poured over the gold and silver granules, in the porcelain jars, and now containing a large quantity of silver in solution, has yet to be disposed of. A solution of chloride of sodium-common salt-is first added to the solution, and a deposit of white powder is the About 7 grains of gold are used in each assay. result. This powder is chloride of silver. The next This small quantity, with the right proportion of process is to free the chlorine from the silver, and silver, which is estimated by the assayer with an this is done by placing it in vats with granules of accuracy attained by incessant practice, is placed in zinc. The chlorine and zinc readily combine, and a cupel-a cup of calcined bone-and deposited in a the silver is set free in the form of a light grey small furnace heated to redness. A strong current powder. This, like the gold, is washed, pressed, of air passes over the contents of the cupel, oxydiz-and formed into "cheeses" worth 800 dollars each. ing the lead. The oxide dissolves the oxides of the These are melted, weighed, stamped, and ready to other base metals, which are absorbed by the cupel, be disposed of as occasion may require. The silver and the result is a button of pure silver and gold. obtained by the above process contains but one part This button, after being hammered and rolled, is of alloy in 1,000. Some silver is so pure that it placed in a bottle partly filled with nitric acid, which requires no "parting," and, after being assayed, is is set in a sand bath. This acid dissolves the silver, sent at once to the Mint. The Assay Office was leaving the gold untouched. When the process is established in this city in October, 1854, and since finished, the pure gold left in the cupel resembles that time over 160,000,000 dollars have passed tinder. It is then annealed, rendered into a com- through the hands of its officers. "Scientific pact coil, called the "cornet," and weighed. The American." weight gives the exact amount of pure gold. Two pieces were, it will be remembered, taken from the metal after it had been melted. Each of these pieces is assayed separately, and the results must, of course, agree. If they should not do so, it is evident that a mistake must have occurred somewhere, and the whole process has to be repeated.

As soon as the assays are completed, the assayer reports to the Assistant Treasurer of the United States, and on his report the depositor is paid. If he desires to receive gold coin, one-half of one per cent. is charged. For gold bars, which are handier for shipment, he has to pay six cents for 100 dollars. For every ounce of pure gold which his deposit has yielded, he receives 20-672 dollars, less the charges stated above. Depositors of silver receive its full value, less what is called the "parting charge," which is about five cents per ounce. Brittle metal

THE "Stationer" states that about forty years ago there lived at Brighton a bookseller and stationer of the name of S. K. Brewer, and he used to place in his shop window piles of paper, beginning at the largest up to the then smallest size, 16mo; but to finish off the pile he cut cards so as to bring them up to a point. Ladies used to go in and ask for that

dear little paper," which induced him to cut paper in small sizes. Then came the difficulty of the place for address, and the result was he invented the envelope, and had metal plates made for cutting them to shape and sizes. This just pleased the ladies, and orders came to him for the little paper and envelopes from all parts. This at length became such a demand upon his time, that he got Dobbs and Co., of London, to make them for him. Such was the beginning of the envelope trade.

THE SIEMENS FURNACE.

THE SIEMENS FURNACE APPLIED TO THE

MANUFACTURE OF CAST STEEL.

O a of Chemical So- most layers.

N the 7th of last May Mr. Siemens delivered

which are thus withdrawn from the regenerators are a positive gain to the heat of the furnace, because, having been in contact with comparatively cold metal, they would be at a heat inferior to that of the upper portions of the regenerators, and would therefore only lower their temperatures.

As the bars sink in the hoppers by their gravity, they are followed up by additional bars until the metal charged amounts to about three tons, all of which will be rendered fluid within about four hours from the time of commencing the charge. The metallic bath is tested from time to time by the introduction of a bar through one of the front doors of the furnace, and if the bath should become thick before the end of the operation, although the heat has been maintained, it will be necessary to introduce an additional quantity of pig metal. All the metal being liquid, a sample is taken out by means of a small iron ladle, and plunged into cold water while still red-hot. In breaking this sample upon an anvil, the temper and quality of the metal may be fairly judged. Its fracture should be bright and crystalline, betokening a very small proportion of carbon (not exceeding 1 per cent.), and the metal should be tough and malleable, notwithstanding its sudden refrigeration. From 5 per cent. to 8 per cent. of spiegeleisen (containing not less than 9 per cent. of manganese) is thereupon charged through the side openings upon the bank of the furnace, and allowed to melt down into the bath, which is then stirred and made ready for tapping in the manner before described. The amount of carbon introduced with the spiegeleisen determines the temper of the steel produced, the manganese being necessary to prevent redshortness, unless Swedish or Styrian iron is used.

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When old iron rails or scrap of inferior quality are charged, the addition of manganese does not suffice to effect the necessary purification of the steel produced, but the perfectly liquid condition of the bath, together with the unlimited time available for chemical reaction, offer extraordinary advantages for the introduction of such materials of the furnace must be sufficient to fuse the sur- as may be found to combine with sulphur, phosface of each layer, that is to say, it must rather ex-phorus, silicon, or arsenic, which are the usual ceed a welding heat to begin with, and rise to a antagonists to be dealt with. The experiments full steel-melting heat at the end of the operation, which I have been able to institute in this direction in order to impart additional solidity to the upper- are by no means complete; nevertheless, I have ciety on the application of his furnace to the manu- of the bath assumes the form of a shallow basin, duction into the bath of litharge, in conjunction facture of cast steel. Mr. Siemens' able lecture being deepest near the tap hole. Some white with oxidizing salts containing strong bases, such dealt at great length with the theory of steel sands, such as that from Gornal, near Birmingham, as the alkaline nitrates, chromates, chlorates, making, and with the more remarkable features in will set under these circumstances into a hard im- stannates, titanates, &c. The choice of the reagents its history; he also described minutely the work-pervious crust, capable of surviving from twenty and the quantity to be employed depend, naturally, ing and construction of his furnace. The most to thirty charges of liquid steel, without requiring upon the quality and quantity of objectional interesting portion of the lecture referred to the material repairs. If no natural sand of proper matter to be removed. By the aid of the process production of steel direct from the ore and the just described it will be possible to convert old iron fusion of steel in an open bed, which we reprorails into steel rails of sufficiently good quality duce here. Our engraving illustrates Mr. Siemens' at a cost scarcely exceeding that of re-rolling them into fresh iron rails. The non-expensive nature of the process may be judged by the fact that extremely little labour is required in conducting it; that the loss of metal does not exceed from 5 to 6 per cent., and that from 10cwt. to 12cwt. of coal suffices to produce a ton of cast steel.

observations.

The furnace employed for the fusion of steel on the open bed is similar in shape to a reheating or puddling furnace; the direction of the flame is from end to end; and the regenerators are placed transversely below the bed, which is supported on iron plates, kept cool by a current of air. The air enters beneath the bed plates in front, and escapes by two ventilating shafts at the back of the furnaces near the ends. This cooling of the bed is very necessary to keep the slag or melted metal from finding its way through into the regenerator chambers. The upper part of the furnace is built entirely of Dinas brick, consisting of nearly pure silica, which is the only material, of those practically available on a large scale, that I have found to resist the intense heat at which steel-melting furnaces are worked; but though it withstands perfectly the temperature required for the fusion of the mildest steel, even this is melted easily if the furnace is pushed to a still higher heat.

There are three doors in the front of the furnace, one in the centre immediately over the tap hole and two near the bridges, through which the bed can be repaired when necessary, and ingot ends and other heavy scraps may be charged in. Sloping shoots are provided at the back of the furnace, through which long bars, such as old rails, may be conveniently charged, and beneath these are openings for charging the pig iron. The upper ends of the shoots is on a level with an elevated charging platform behind the furnace. The bottom of the furnace is formed of siliceous sand, which answers exceedingly well if properly selected and treated.

Instead of putting moist sand into the cold furnace, as is usually done in preparing the bottoms of furnaces for heating or melting iron or copper, I dry the sand and introduce it into the hot furnace, in layers of about lin. thickness. The heat

quality is available, white sand, such as Fontaine-
bleau sand, may be mixed intimately with about
25 per cent. of common red sand, to obtain the

same results.

In tapping the furnace the loose sand near the tapping hole is removed, when the lower surface of the hard crust will be reached. The lowest point of this surface is thereupon pierced by means of a pointed bar, upon the withdrawal of which the fluid metal runs out from the hottest and deepest portion of the bath into the ladle in front of the furnace.

M. Le Chatelier now proposes to mix the natural bauxite, of which the bottom of the experimental furnace at the works of MM. Boignes, Rambourg, and Co., near Montlucon, was first made, with about 1 per cent. of chloride of calcium in solution, to calcine the mixture and to form it into moulded masses of highly refractory material. A hard bottom being thus prepared, and the heat of the furnace being raised to whiteness, it is ready to receive the materials to be melted. If these materials consist of bar iron, or of old iron and steel rails, they are cut into lengths of about 6ft., and are introduced into the furnace through slanting hoppers B from the elevated platform at the back, so that their ends rest upon the sand bottom forming the bath.

If the capacity of the furnace is such that charges of 3 tons can be formed, about 6cwt. of grey pig iron is introduced through the ports or short hoppers below the main charging hoppers before mentioned. As soon as a bath of pig metal is formed, the heated ends of the rails or bars begin to dissolve, causing the bars gradually to descend. By partially closing the mouths of the charging hoppers a regulated quantity of flame is allowed to escape from the furnace, in order to heat the descending bars of metal previous to their entry into the melting-chamber, the object being to maintain the high temperature of the furnace, notwithstanding the constant introduction of cold metal. The escaping products of combustion

Although I have succeeded in producing malleable steel from ordinary English iron by this process, it would be unreasonable to expect steel of really high quality in using those materials which are already contaminated in the blast furnace; and I am sanguine in the expectation of producing cast steel superior in quality, and at a low cost, directly from the better description of ores, such as the hæmatites, magnetic oxides, and the spathic carbonates. My experiments in this direction extend over several years; and last year I sent a few bars of steel produced from hæmatite ore to the French Exhibition, which had stood a high test in Kirkaldy's machine. A "grand prix" was awarded for this and other applications of the regenerative gas furnaces. Having tried various modifications of the furnace I have arrived at a form of apparatus not dissimilar to the one just described. The furnace and tapping arrangements are, indeed, the same, except that for the slanting hoppers vertical hoppers over the middle of the bath are substituted, in which the ore gradually descends. Each hopper is formed of a cast-iron pipe, supporting a clay pipe, which is attached to it by means of a bayonet-joint, and reaches down into the furnace, while the cast-iron pipe rests with its flange on the charging platform.

A fire space is provided surrounding each hopper, through which flame ascends from the furnace, and is allowed to escape in regulated quantities near the upper extremity of the retort, the object being to heat the latter and the ore contained in it to a red heat. A wrought-iron pipe descends into each hopper from a general gas

tube above, through which a current of ordinary producer gas is forced in amongst the heated ore. The propulsion of the gas is effected most conveniently by means of a steam jet in the gas tube leading from the main gas channel to the top of the furnace, care being taken to effect a total condensation of the steam by passing the gas finally through a small scrubber, in which water trickles over pieces of coke. In this way the gas is at the same time purified from sulphurous acid, the sulphur of which might otherwise combine with the reduced ore.

ances are necessary. These are located in the machine shop, an apartment 150ft. in length and 50ft. in breadth, both sides of which are lined with turning lathes, slotting and boring machines, and such One of the turning like, of extraordinary size.

the vibration of the ground under his feet, caused by the incessant blows of the steam hammers; and a peep inside reveals a scene of extraordinary activity. We shall briefly describe what came under our observation as we were shown through the work by one of the proprietors, and thus endeavour to convey lathes is said to be the largest in the world; and some idea of what goes on in the place. The first some idea of its dimensions and form may be obdepartment we entered was the rolling mill, which tained from the fact that the crank shaft of the is 300ft. in length, and 150ft. in breadth. At one end "Monarch," though weighing thirty-two tons, was of the mill are arranged twenty-two puddling furnaces, turned in it without taxing its capabilities to the and half-a-dozen re-heating furnaces. The rolling utmost. Some of the iron shavings lying about the and other machines are driven by a pair of horizontal vast machine were fully lin. broad and in. thick; engines of 300-horse power. The fly-wheel of the yet these were turned off with apparently as little engines is eighteen tons in weight, and it makes 100 effort as if the material had been wood instead of iron. The furnace is charged in the following manner: revolutions in a minute. The steam is supplied by One of the boring machines is sufficiently powerful -The hoppers and gas pipes being placed in posi- fourteen vertical boilers heated from the puddling to drill a hole 10in. in diameter through a solid tion, about a cwt. of charcoal is charged through furnaces. The iron is first rolled into bars, then cut block of iron; and the largest slotting machine can each hopper to form a basis for the ore with which up, re-heated, and either rolled into ship and boiler send off chips a pound or two in weight. When the these are afterwards filled. About 10cwt. of pig plates or wrought into pieces suitable for the forge. work leaves this department, it is generally quite metal is charged through the ports at the back or At one time the firm devoted attention to the making ready for being fitted into its place. This firm front of the furnace, which, upon being melted, of armour plates, and their specimens stood the test pay nearly £40,000 a-year in wages; and in all deforms a metallic bath below the hoppers. In the of competition with those of English makers most partments of the establishment, 15,000 tons of iron, meantime the ore in the lower parts of the hoppers, creditably; and but for the want of convenience for and 60,000 tons of coal are annually used.-"The being heated in an atmosphere of reducing gas, distant-Messrs. Rigby and Beardmore would have carrying the plates-the nearest railway being a mile Ironmonger." has become partially reduced into metal sponge, obtained a fair share of patronage from our own which, in reaching the metallic bath, is readily and other governments. The machines are capable dissolved in it, making room for the descent of the of producing plates 8in. thick, and some of the plates superincumbent ore, which is likewise reduced in made of that thickness have weighed twelve tons each. its descent, and dissolved in due course, fresh ore At some of the puddling furnaces a new invention being continually supplied on the charging plat- was being tested, and we were told that the most form. The dissolution of the reduced ore proceeds satisfactory results were being produced by it. Its with extraordinary rapidity, but is practically object is to hasten and render more perfect the limited by the time necessary to effect the reduc-puddling process, by injecting a current of air at tion of the ore in the hopper, which occupies making the puddling bar hollow and affixing to the high pressure into the furnace. This is done by several hours. It is, however, not essential that outer end of it an india-rubber tube communicating the ore should be thoroughly reduced before reach- with a powerful air-pump. The patentee is Mr. ing the bath, because the carbon contained in the Richardson, of Glasgow; and the advantages gained cast metal serves also to complete the operation. by the contrivance are that a charge of the furnace can be puddled in fifteen minutes less than the time required by the usual process, and that the iron produced is purer and tougher.

I prefer to employ a mixture of hæmatite and spathic ore, containing the elements for forming a fusible slag, which will accumulate on the surface of the metallic bath, and may be from time to time removed through the centre door. If the ore contains any silica it is necessary to add some lime or other fluxing materials, but it is desirable to employ ores containing little gangue, in order not to encumber the furnace with slag, reserving the poorer ores for the blast furnace. The ore should, moreover, be in pieces ranging from the size of a pea to that of a walnut, in order to be pervious to the reducing gases. If ores in the form of powder are employed, it is necessary to mix them with about 10 per cent. by weight of light carbonaceous materials, such as dry peat, wood, or charcoal.

process

The forge or smithy is nearly as large as the rolling-mill, and its fittings are of the most gigantic fifty tons each; four, forty tons each; and four, kind. There are two steam cranes, capable of lifting twelve tons each; and these are so arranged that a shaft or other piece of work may be passed from one to the other all over the shop. There are fifteen steam hammers, varying in weight from seven tons to two. Finished shafts-that is finished so far as the hammering was concerned-were lying about in all directions, and so delicately had these been operated upon by the hammers that the surfaces were so smooth that turning would seem to be almost superfluous. Yet they were destined before leaving the place to be fitted into a lathe and turned The metallic bath having sufficiently increased with the greatest exactness. In the heating furnaces in the course of from three to four hours, the and under the hammers were a dozen more heavy supply of ore is stopped, and that contained in the jobs in the shape of crank-shafts, rudder frames, hoppers is allowed to sink. Before the hoppers are and such like; and as these were in all stages of empty, a false cover of cast iron lined with clay progress, a glance at them made plain the whole at its under side is introduced, being suspended instance, a piece of iron 8ft. or 10ft. long, and of suitof forging. In making a crank shaft, for from above by a strong wire, in order to preventable diameter, is used as a "haft" or handle. At the access of flame to the interior of the empty one extremity it is fitted with cross-bars or levers, hoppers. Charcoal and ore are filled in upon the by which it may be turned on its axis; and the other top of this false cover, and, on cutting the wire, end is shaped conveniently for having smaller pieces afterwards form the commencement of the suc- of iron welded to it. The welding end is placed ceeding charge. in a furnace, and in about an hour and a-half is raised moved about is fitted with a chain collar or sling, in to a welding heat. The crane by which the iron is the loop of which the iron rests. The collar works in a pulley attached to the chain of the crane, and moves easily, so that the shaft may be readily turned on the anvil. When the proper degree of heat is attained, the stopping of the furnace is removed, the steam crane put in motion, and the gigantic bolt is swung on to the anvil of the steam hammer. Several large slabs of iron, similarly heated in the "face" of the "haft." A signal from the head another furnace, are then brought out and laid on forgeman, and the hammer drops upon the glowing mass, and a dazzling shower of sparks fly off in all directions. Again and again the hammer descends, the iron meantime being carefully moved about, so as to have the whole wrought into a homogeneous mass. Gradually the iron assumes a dull colour, but not before the desired end is obtained. It then goes back to the furnace, comes forth glowing, has most difficult part of the work is the formation of another addition made to its bulk; and so on. The the crank-piece, which is forged solid, and forms a huge square projection on one side of the shaft. When the shaft has acquired the proper dimensions it is allowed to cool, and the haft-piece is cut off to be used again. As the shafts are turned down until a good surface is obtained, an extra inch or so is allowed in the forging. The heaviest work on hand at the time of our visit were the shafts for to Napier and Sons for the British Government. two ironclad rams which are being built by Messrs. These shafts were upwards of 14in. in diameter. All shafts are made in lengths of about 20ft., and these are made with flanged ends so that they may be firmly united.

When all the ore has disappeared the metallic bath is tested as before described in reference to the melting of scrap. If it should be partially solidified, cast iron is added to re-establish complete liquefaction; but if, on the othor hand, the bath contains an excess of carbon, oxidizing agents may be added, as before described, in requisite proportion. From 5 per cent. to 8 per cent. of spiegeleisen is then added, and the furnace is tapped as already described. The quality of the steel produced is chiefly dependent upon the quality of the ore, but considering that ores of great freedom from sulphur, phosphorus, or arsenic, can be had in large quantities, this process contains all the elements for producing steel of high quality. Having tried a variety of ores, I do not attach much importance to their precise composition, so long as they are comparatively free from gangue, and from sulphur aud phosphorus, the heat being sufficient to reduce the most refractory. My experience is, however, as yet limited to experimental working.

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THE PARKHEAD FORGE. HE Parkhead Forge, Glasgow, is an extensive and boys, but in consequence of the heavy nature of the work, the proportion of boys to men is smaller than in other branches of iron manufacture. The buildings cover several acres of ground, and are built in a most substantial style. On approaching For dressing and finishing such huge pieces of the entrance to the Forge, the visitor is startled by iron as we have described, special and costly appli

THE RAILWAY MOVEMENT IN AMERICA.

HERE are probably now in operation at least

37,500 miles of railway in the United States, about one mile of railway to every million of inhabitants, and though this would seem a fair amount of with unabated force. From the fact that the great supply, yet the construction movement still goes on proportion of the gross amount is in the Atlantic or seaboard, and in the contiguous Central and Northwestern States, it would be supposed that the movement in these localities would have about ceased; but the facts show the contrary. In the New England States and the States of New York there is now being constructed, or at least commenced, an amount of full 1.500 miles, at an estimated cost of at least 60,000,000 dollars. Some of these are extension the line from Oswego from Rondout; others are lines, like that to Hudson River from Boston, and connecting or cross lines, and many others spur or branch lines, for merely local convenience. There seems to be no limit to the demand in the thickly settled communities, and as long as the capital can be procured and charters obtained, we must expect railway construction to continue until the entire land is grid-ironed into very narrow spaces. We are now speaking of the more densely settled states between the seaboard and the Mississippi River, and the lakes; but, as the population increases in the states away from the seaboard, we shall find the same state of things to exist. The main or through lines are now pretty well indicated, but more will yet be added, and the branch or spur lines will, in all probability, be as thick as they are in New With a population of 37,000,000, the England. full 1,500, and as population increases, we see no miles of railway annually constructed will average reason why railway construction should not increase in about the same ratio. In all human probability, in the year A.D. 1900, at the present rate of increase, there will be in operation in the United States, at least full 90,000 miles of railway, representing a gross cost, at 40,000 dollars per mile, of 3,600,000,000 network of railways will require vast armies of men; dollars. To iron, equip, and reconstruct this vast machine shops, iron mills, forges, steel works, will have to be multiplied, and we trust long before that time arrives that the labour, mechanical, and manufacturing skill of the country, will be found ample to meet the demands, so that we need not be required to depend upon foreign supply to iron or equip our great national system of highways.

We have placed the estimate of annual progress of the past two years, and have allowed nothing for at a very low figure and within the actual experience the presumed increase in the Southern States, whenever these shall recover from the effects of the recent conflict. In 1870 the Pacific Railway will be running. and the shores of that ocean will soon be covered with cities and trade marts rivalling those on the Atlantic. At least two more through lines will be constructed, one on the north and one at the south, and these will in time be crossed and interlaced by The increase of and virtual monopoly of the best numerous lines on what is now unoccupied territory. portion of the commerce of the East with Europe, by the United States, will give our railway movement a great impetus, besides incidently fostering and developing all the other great business interests of the country. The country should be prepared by proper legislation, by the development of its iron mines, its steel manufactories, its machine shops and skilled labour, to supply the extended demands that this conducted with great increase of railway lines will make.

In

ordinary business shrewdness and common sagacity, need there be any fear of failure in the future. A proper fostering on the part of legislation will in time make this country entirely independent of foreign manufacture either in iron, steel, or other machinery." U. S. Railway Times,"

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TO CORRESPONDENTS.

of £1 1s. 8d. yearly, or 10s. 10d. half-yearly payable in
THE MECHANICS' MAGAZINE is sent post-free to subscribers
advance.

All literary communications should be addressed to the
Editor of the MECHANICS' MAGAZINE. Letters relating to
the advertising and publishing departments should be ad-
dressed to the publisher, Mr. R. Smiles, MECHANICS' MAGA-
ZINE Office, 166, Fleet-street, London.

ments should reach the office not later than 5 o'clock on
To insure insertion in the following number, advertise-
Thursday evening.

We must absolutely decline attending to any communi-
cations unaccompanied by the name and address of the
writer, not necessarily for insertion, but as a proof of good
faith.-ED. M. M.

Advertisements are inserted in the MECHANICS' MAGA

TO THE EDITOR OF THE "MECHANICS' MAGAZINE."
SIR-I am obliged by your notice of the meeting
at the City Terminus Hotel, on Thursday week, on
the subject of my deep sea telegraph cables, in
your paper of the 10th inst. The following remark,
however, requires a word of explanation. You say,
"Captain Rowett comes before the public under
great disadvantages, not having a single instance of
the practical adoption of his system to point to
during the ten years his patent has run." My
answer is simple and unmistakable. The two cables
laid by the Atlantic Telegraph Company, with the
aid of the Anglo-American Company, are my patent
cables. They are described in my specification as
clearly as words could describe them, and no one
but myself has laid claim to their authorship. In
all the celebration feasts that followed the successful
laying of the cables no reference was made to their ZINE at the rate of 6d. per line, or 5d. per line for 13 inser-
inventor by any of the speakers, which you will tions, or 4d. per line for 26 insertions. Each line consists
admit was remarkable, because their success mainly of about 10 words. Woodcuts are charged at the same rate
depended upon having the right description of cable. as type. Special arrangements made for large advertise-
On these occasions the honour and credit were
monopolized by the parties who laid the cables and A. L.-W. M. R.-G. W. H.-R. J.-W. N. G. E. P.-F. R.
RECEIVED.-J. J.-W. C.-J. R.-H. T. R.-E. N. B.-
those who brought together the shareholders to pay B. T. H.-J. G. T.-Messrs. W. G. and Co.-J. E.-K. S.
for them. This was perfectly right so far as it went.-T. R.-D. H. R.—T. H.-B. T.—M. S.—T. H. D.—R. J.—
The author of the cable was for the moment ignored. W. W. H.-J. F. H.-D.B.-T. J.-Messrs. F. and C.-J. R.
The subject was a sore one, and might have marred R. B. J.-M. H. W.-J. A.-E. M. C.—D. M. L.-H. R. O.
the harmony of the meetings. His share of the
honours would keep, and only remained unsettled the receipt of several books sent for review, notices of
NOTICE TO PUBLISHERS.-We have to acknowledge
because the distinction must be accompanied with which have been kept out by press of other matter, but
some substantial compensation in the form of a which will shortly appear.
patent right, for, happily, well-observed laws protect
inventors of instruments which contribute to the
public good, and a deep-sea cable which had been
for years pressed upon the attention of the Atlantic
Telegraph Company must not be an exception to so
good a legislative provision.

From the year 1857 I had been urging the Atlantic Company to adopt my light hempen cable, which would lie at the bottom of the sea as still as the heaviest iron cable could lie, and could be safely laid at half the cost of the cables they have chosen. But in stead of making the pure and simple hempen cable-which, for every scientific reason, is indisputably the best-in despite of both science and common sense, they made their first cable envelope entirely of iron, their second cable a mixture of iron and hemp loaded with tar, their third cable of hemp and iron wire without the tar. In the last two cables Manilla hemp was used, and so the specific gravity of their cable was reduced precisely as my patent provides. The two last cables are carefully specified in my patent of 1858, in anticipation of the probability of the Atlantic Company making step by step from iron wire envelopes to first a mixture and then to lighter and lighter cables.

ments

-W. E. B.-H. R. F.

formed into parallels, galleries, mines, and other works in readiness for the operations, which will take place in the course of the ensuing month.

THE new navy hospital to be established at Yokohama, for which provision is made in this year's estimates, will contain about 30 officers and 120 men. By this establishment in the healthier climate of Japan the costly and unsatisfactory hospital ships at Hong-Kong and Shanghai will be superseded, and it is also hoped that the present necessity for invaliding home officers and men from both impairs the efficiency of the service and enthe squadron on that station-a proceeding which tails a heavy annual expenditure-will be removed. The total estimated cost of this hospital is £25,000.

Miscellanea.

MR. COOPER, the explorer, has reached the confines of Western China, and, according to the last advices, was fifteen days' journey from Thibet.

THE railway offices of Dairsie Station, on the North British line, were destroyed by fire on the night of Tuesday week. They were constructed of wood.

THE number of visitors to the Patent Office July 11, was 7,956; total number since the opening Museum, South Kensington, for the week ending of the museum, free daily (May 12, 1858), 1,329,258. A SOLDIER of the Royal Horse Artillery was struck by a flash of lightning while walking in Woolwich on Sunday evening. He was rendered

quite blind, and had to be led to the barracks.

ADVICES from St. Etienne announce that a great fire has destroyed the velvet-ribbon manufactory belonging to MM. Descours and Co., at St. Paul-enCornillon. The loss is estimated at 500,000 francs, besides 300 hands being thrown out of employment.

Habal, Military, and Gunnery Items. Office at the Cape. It weighs 15 carats, and is

has

THE American transport ship "Guard". arrived at Civita Vecchia to embark a quantity of statues and works of art purchased by Admiral Farragut for various museums in the United States. ACCORDING to a return just published, it appears that the unclaimed wages of deceased seamen. paid into the Consolidated Fund during the year 1867, amounted to £7,783 6s. The fines and forfeitures for desertion, &c., amounted to £349 11s. 7d.

A LARGE diamond, found by a Griqua near the Vaal River, has been forwarded to the Colonial valued at about £400. Several others have been found in the vicinity of the Vaal River.

THE "Moniteur " publishes a list of medals conferred at the instance of the Minister of the Interior:-Two gold of the 1st class, three of the 2nd, four silver 1st, and 97 silver second, for acts of devotedness connected with the saving of life during the months of March and April.

FIFTY house-sparrows have been received from Britain by Mr. W. Rhodes, of Quebec, who has turned them loose in the Governor's garden, below THE Italian Chamber of Deputies have just passed the Wolfe and Montcalm monuments. Mr. Rhodes a vote of 3,000,000 lire for the armament of the iron-is of opinion that this bird may be acclimatized so clad fleet and the conversion of the marine rifles as to remain during the whole year. into breech-loaders. During the debate the Minister of Marine stated that the Italian ironclad fleet was in perfect order, and left nothing to be desired. The Government had determined to arm the fleet with Armstrong guns.

WHEN the French military medal of the Legion of Honour is given to privates or non-commissioned officers a pension of 100f. is attached to it, but there is no pension when it is given to general officers. There are also establishments attached to the Order of the Legion of Honour for the education of the daughters, nieces, and sisters of the members. The principal or central one is fixed in the large buildings of the famous Abbey of St. Denis, confiscated at the Revolution. It was founded by Napoleon in the Chateau of Ecouen, and was placed under the superintendence of Madame Campan.

The two last cables have a single iron wire wrapped in several strands of Manilla hemp. Compared with the first cable, which is iron, this is, of course, light. But of what use can be the iron wire? They admit its own weight in three miles' depth destroys itself, and they admit that oxidation would destroy the hemp with which it is surrounded The pure and simple hemp envelope is, therefore, the best, and the cables that are laid and doing good service are indisputably my patent cables, and all that I need say is that they are not the best is amply proved. But if any merit can be found in placing HER MAJESTY'S yacht "Victoria and Albert," a wire in the centre of each strand I am willing to Captain His Serene Highness the Prince of Leiningen, meet the wishes of any party; though it was included recently returned to Portsmouth from a cruise beyond in my patent to protect my invention from piracy, the Arctic circle, the purpose of which still remains I do not recommend it. Your numerous readers will one of the official mysteries. This magnificent vessel be glad to see by what I have stated that there are is, we believe, the first of her size and costliness hopes of having my light, inexpensive, and efficient which has made the attempt to penetrate the dancables laid, that the cost of messages over long deep-gerous fiords and intricate channels of the Norsea lines may be as cheap as those on land. To this wegian coast. The ship left Portsmouth on the 1st end we must hope the press will give a helping hand. June. It is surmised that the trip was undertaken I trust this explanation will be allowed a space in as a trial cruise, with the view of its being repeated your next number.-I am, Sir, yours, &c., on some future occasion for the benefit or pleasure London, July 11. W. ROWETT. of the royal family. [With regard to the broad question with which Captain Rowett's letter opens, we can only say that we were present at the meeting, and put the plain question "Can you point to any examples of the practical application of this system?" receiving a plain answer in the word "No." The chairman also referred to the same fact as being a misfortune for Capt. Rowett, which the captain tacitly admitted. -ED. M. M.]

CIVIL AND MECHANICAL ENGINEERS'
SOCIETY.

A PARLIAMENTARY paper issued on Saturday gives an account of the army prize money paid to the Commissioners of Chelsea Hospital from Jan. 18, 1809, to Dec. 31, 1867, as follows:-To 5 per cent. deducted from prize money, £2,325 6s. 11d.; to cash arising from shares of prize money awarded to the army, £1,508,822 3s. 6d. ; to cash arising from dividends, &c., £260,76918s. 6d. ; total, £1,771,917 9s. 2d. By cash refunded, £993,317 19s. 4d.; by expenses in executing acts, £64,876 10s. 10d.; by sums paid to Royal Hospital and transferred to the Exchequer, £638,439 8s. 9d.; by sums paid to the Commissioners for Works and Buildings, £40,000; balance, £35,283 10s. 3d.; total, £1,771,917 9s. 2d. In addition to the balance here stated there is in the Bank of England £31,225 14s. 1d. to the credit of the army prize account, and in the funds £65,000 Three per

SIR,-In reference to your notice of the annual meeting of the above Society, given in your paper of the 4th inst., you state that this Society has been established for the mutual benefit of assistant engineers and pupils in both civil and mechanical en-Cent. Consols. gineering. Permit me to say, that in addition to PREPARATIONS are being made at Chatham for these classes of the profession, the Society is largely patronized by men who practise engineering on their own account, and that at present the names of

carrying out some siege operations on a scale of
magnitude never previously attempted. The whole
of the lower portion of Chatham lines has been

A FINE fresco has just been discovered in the church of Santa Maria del Giardino, which is now being demolished. This fresco, which is in a good state of preservation, represents St. Antonio of Padua, and is attributed to the painter Suardi.

AT the meeting of members and associates of the Royal Academy on the 30th ult., for the election of a member in the place of Baron Marochetti, deceased, Mr. F. Leighton was chosen by a large majority. Mr. Leighton was elected A.R.A. in July, 1864.

THE authorities of the South Kensington Museum are forming a collection of engraved portraits, and a considerable number of those which have already been obtained are now on view on the upper floor of the National Portrait Exhibition at Kensington.

SOME miscreant recently conveyed a quantity of poisoning matter into the park of the Bishop of Durham at Auckland Castle, and put it into the River Gaunless, which runs through the park, for the apparent purpose of poisoning the fish with which the river abounds, and in which diabolical act, we regret to say, he partially succeeded.

SEVERAL Italian journals state that Father Secchi, the constructor of the great astronomical clock so much remarked at the Universal Exhibition of 1867, has discovered a motive power, lighter, stronger, and more economical than steam. They add that the learned Italian is stated to have laid his invention before the court of Portugal, which is disposed to purchase it.

A CERTAIN doctor lately stated for the information of the Board of Education at the Normal State University of Illinois that the atmosphere was composed of oxygen and hydrogen. He accounted for the explosion that takes place, consequent to a discharge of electricity, on the ground that, as he believed, the electricity decomposed the air, leaving the hydrogen as an explosive compound behind!

A NOVEL race was run last week between a horse and car and a velocipede. M. Carrere in a one-horse car, and M. Carcanade in a velocipede, started from Castres at twelve, and the victory was to be decided in favour of the person who first arrived in Toulouse. The race was a very keen one, M. Carrere having arrived in Toulouse at 6, and M. Carcanade at 6.25. IT is stated that petroleum oil possesses the highest efficacy as a destroyer of all kinds of insects injurious to plants or animals, and the less purified, and, consequently, the cheaper it is, the better. Thirty parts should be mixed with 1,000 of water, and applied where required. The "Medical Times" states

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