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flow in and out, the accident would not have happened. There were two stand-pipes to the watercasing, which, if open, would have prevented it. When the accident took place he had saved himself from being scalded to death by throwing himself down in the stokehole and covering his face with his hands. Witness knew that the engines were under the charge of Mr. Russell. Mr. Russell was on the bridge giving orders to his men below.

The Coroner asked the solicitor to the company whether any one was in attendance on the part of

Mr. Scott Russell?

one seemed to know how, when, or by whom the cock was shut. Two or three days before the ship sailed, the "stand-pipe" not being high enough, a piece was added to it, so that up to that time the cock must have been open. It was supposed to have been closed by some workinan for some purpose, and not to have been again opened. By a Juror.-There was no safety or other valve to show there was pressure in the cases, as the pipe should always be open. Mr. Dickson was the engineer under Mr. Scott Russell directly responsible for the making and working of the engines. The engineer believes the cock never was opened from the time of leaving the river. If the cock had been taken off the accident could never have happened. The cock was put on to test the cases by hydraulic pressure, and had not been removed. The cock could not have been closed by the force of the explosion, or, indeed, witness could not conceive the accident occurring.

The court then adjourned to 9 o'clock on Saturday morning. The jury and the Coroner proceeded to examine the part of the ship where the

WEYMOUTH, WEDNESDAY, Sept. 14. To-day, at 2 o'clock, the adjourned inquiry was resumed. The investigation appeared to excite no great amount of interest, and the court was almost empty throughout the entire proceedings. Mr. J. Scott Russell, in compliance with a wish expressed by the Coroner, came down from town to attend the inquest.

Mr. John Dickson, foremen to Mr. Russell, and under whose superintendence the machinery of the paddle engines was fitted, was also present, and Mr. M'Lennan, the chief engineer of the Great Eastern.

Mr. Newman (of Freshfields and Newman) attended to watch the case with Mr. Scott Russell. At the commencement of the proceedings Mr. Leverson, the solicitor to the company, said he wished to correct an error which had appeared in some of the papers to the effect that he (Mr. Leverson) had stated at the previous inquiry that Mr. Scott Russell had had ample notice to attend the opening of the inquest, but had not done so. In fact, what he had stated was exactly the reverse, namely, that Mr. Scott Russell had had no notice of the inquiry; that he was at the time in London, on the company's business, and could not possibly have been in attendance.

Mr. Leverson stated that there was no one. Mr. Brereton, one of Mr. Brunel's principal engineers, was called to give evidence as to the probable cause of the accident. He stated that Mr. Brunel intended to accompany the ship on the trial trip, but in consequence of his illness witness accompanied the ship on his behalf. The accident occurred at six p.m. on Friday afternoon, when the ship was off' Dungeness. When the explosion took place witness was near the paddle-accident occurred. boxes. The foremost funnel was blown up above the deck, immediately followed by a shower of splinters and pieces of glass. Went forward and found the funnel lying on deck in two parts, and on looking down the gratings leading to the boiler rooms heard men crying for help and water. A good many of the passengers were there at the time, the fire hoses were laid on, a supply of water obtained to extinguish any fire that might have occurred; men then went below and brought up the wounded. As soon as the confusion was over examined the broken funnel on deck. On the following morning, according to the direction of the chairman, witness, with other engineers on board, examined the place where the explosion took place, to make a report as to the cause of the accident. Witness was accompanied in his examination by Mr. M'Connell (the engineer of the North-Western Railway), Mr. Scott Russell, Mr. Smith (the inventor of the screw propeller), Mr. W. Smith (a civil engineer), and Mr. Bates, who represented the firm of Boulton and Watt. Witness and those with him came to a conclusion as to the cause of the accident. The double-funnel casing was not always applied to other steamboilers. The fact of the woodwork around the funnel being blown away led witness to see the cause of the accident without the drawings or explanations. They ascertained that the funnel was double for 40 feet of its length, the inside being 6 feet diameter, and the outside one 7 feet, leaving a space of 6 inches between the two all round. The water was contained between the two; the explosion took place about half-way down, near the lower deck. The inner casing was collapsed, and the outer one burst out. The object of the casing was to prevent the water being led direct to the boilers. There was an apparatus provided to prevent any excessive pressure accumulating in the water-jacket. This apparatus consisted of a "stand-pipe," which was carried to near the level of the top of the funnel, and communicated with the water-jacket, constituting a safety-valve. Being open at the top, as soon as the pressure increases it runs out of the "standpipe." The height of the column of water regulated the pressure in the jackets. From inquiry they learned that the feed water for the boiler was sent direct to the boiler without passing through the funnel, as the donkey engines did not work satisfactorily; one of them being disabled, the other had to do the work of two. That accounted for the fact of the communication between the boilers and the casing being shut off. An explosion ought not to have occurred if the "stand-pipe" was in operation, Their attention was called to the state of the stand-pipe, and they found at the bottom of it a plug capable of being turned. It was shut off, leaving no vent for the steam generated in the case. If the "stand-pipe had been in operation, or if the feed was continued through the jacket, the explosion would not have occurred. The steam must have gone on generating till the cylinder burst. No

After a few words from Mr. Scott Russell, who explained the cause of his unavoidable absence [and, as reported in the Morning Star, added that "he was decidedly at issue with the company upon some points relative to the inquiry"],

The Coroner said that, on the opening of the inquest, he had at once considered that it was a case which ought to be adjourned, in order that the jury might have the assistance of some of the surveyors from the Board of Trade He had accordingly communicated with the Board of Trade, and received a letter in reply the previous day which stated that it was impossible that Captain Robertson, the Surveyor-General, could attend the inquiry before Saturday next. He, therefore, thought that, under those circumstances, it would be most advisable that the jury should have the benefit of the experience of those officers, and, with their permission, he would adjourn further proceedings till Saturday morning at nine o'clock. He (the Coroner) trusted that both the company and Mr. Scott Russell would be ready on that occasion with any evidence which could throw the smallest light upon the causes which had led to so disastrous an accident.

One of the jury said that they hoped every effort would be made to discover the man who had turned off the cock or valve which led from the stand-pipe into the stokehole.

Mr. Scott Russell said it would be proved by witnesses that the cock of the valve was open on Tuesday, and when the vessel left the river on Wednesday.

Mr. Leverson intimated that the company were in no degree responsible for what had taken place, and the evidence adduced had established

this on the company's behalf. He had no desire to call further evidence unless wished for by the court.

The Coroner said it was most likely the jury would like to examine Mr. M'Lennan the chief engineer.

The inquiry was then adjourned till Saturday morning.

The Special Correspondent of the Times, who is now at Weymouth, states that "the repair of the damages inflicted by the explosion has already commenced, Mr. Scott Russell having contracted to restore the whole for 5,000. If it should turn out that either of the forward boilers has been injured, 5,000l. will hardly suffice for the entire restoration. From the fact of there having been no escape of steam from either of the boilers at the time of the explosion, when there was a pressure on each of 221b., it is believed that they have escaped without material injury. The mere joinery of the cabin fittings and the redecoration of the grand saloon can, and doubtless will, soon be completed. With the ironwork, however, it is a different affair. All this must be executed in London from the working drawings of the vessel, and sent down piecemeal by rail to Weymouth, where it can be bolted together on board the ship. Mr. Scott Russell's contract is to finish the whole ship in her former state as she left the river within three weeks."

HOW TO MAKE A RIFLE BARREL. THE barrel of a rifle when turned and bored to its finished dimensions is so different a thing from what it was originally in the hands of the smith that its intermediate stages of manufacture may well be described. The problem which has to be solved by the workers at Enfield, and other places which contract with that vast establishment is, how to convert plates of the finest Wedgebury iron, 13 inches long, 9-16 inches thick, and having bevilled edges, which make the sides vary in width from 5 in. to 5 in. respectively, into a slight but strong tube capable of withstanding the shock within it of innumerable discharges of gunpowder, and of directing unerringly a bullet of lead to a mark 1,000 yards distant from its muzzle.

The plate or "skelp" of iron intended for conversion into a barrel has, in the first instance, an almost white heat given to it, and is then passed between a pair of corrugated rolls, the upper roll having semi-circular projections running latitudinally around it, and which fit flutings sunk into the lower roll. The effect of this pinching is to bend the barrel plate longitudinally. It is next passed between double flutings on the same rolls, and this operation makes a cylinder of the "skelp," minus the welding. The bevilled edges are made, however, to approach each other for this purpose, and welding is the next process A rod or maundril of iron about ths in diam. is passed through the orifice of the "skelp," and it is then placed in a reverberatory furnace. When sufficiently hot for the purpose, it is taken to the rolls for welding and drawing out to length and shape. These rolls and their framings resemble much those ordinarily used for rolling iron. There is, however, an important difference-the grooves or flutings upon them are turned out eccentrically with the axis of the rolls. This is for giving the requisite taper from muzzle to breech of the barrel. When the heat is sufficient, which of course practice enables the workman to decide, the barrel is withdrawn by aid of the maundril from the furnace, and laid on an iron rest in front of the mill. The operator now watches carefully his opportunity to thrust it into one of the grooves of the running rolls at a moment when they are prepared to administer the proper pinch for tapering the barrel. A series of these grooves, each smaller than the other, now receives the gradually welding and elongating barrel, until the gauged recess in the rolls finishes the rolling pro

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a guard attached to it coming in contact with the rest, a boy stationed at the back of the rolls receives in a pair of tongs the barrel only, the maundril remaining behind for another operation. This boy, whilst the heat is still upon the barrel, roughly straightens it upon an iron surface. After this it is placed under a power press provided with beds or swedges of the same length as the barrel, the lower of which is horizontal and stationary, and the upper one rising and falling by means of a central joint, which allows it to give" to any irregularities. Supposing all to be sound and satisfactory so far, the next operation will be that of "lumping," or having the cone seat welded on. This is rather peculiar, and demands especial observation. A nice heat is taken on the breech end, and a piece of iron of sufficient dimensions is put on the particular place where it is needed by hand. Then another heat is taken on all together, and whilst in a soft state a maundril is driven into the breech end. It is next placed between dies of the form required, and repeated blows from a trip hammer brings the cone to its proper shape.

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workman—should be sufficient for the purpose of making an accurately parallel hole through a rifle barrel; but it is so. One end of the square bit fits a socket, and is made to revolve to the tune of something like 300 revolutions per minute. On two sides of the squares of the bits strips of deal wood are placed, and it is astonishing to note the perfect truthfulness attainable by these primitive means. Of course the gauge is put in requisition when this boring, for which oil is the lubricator, is completed.

The chamber at the breech-end is next attended to, aud a rose-faced pin-drill is the implement used for boring it out. Afterwards the breechpin is secured to it, and then the proving is commenced. The inspector, whose duty is momentous, at this stage, too, steps in and examines every part of the workmanship and material. Passing this ordeal, the barrels are now ground on an ordinary grindstone to a gauge. Sundry operations follow, the lump or cone seating is shaped up by a cutter, and brought nearly to a finish-the breechpin is also now brought into form by similar This machine is of American invention, and it means. Indeed, revolving cutters or "mills" are is very effective. Its principal parts are of wood. the universal tools at Enfield, whilst the variety of The hammer itself, or lever, is hung on journals, names given to them for identification is amusing. the end carrying the die being by far the heaviest. The barrels are next drilled and tapped to reA disc, fitted with a number of studs on its out-ceive the nipple, then clamp-milled about four ward diameter, lies at right angles with the other inches up from the middle, and on each side of the end of the lever. The disc revolving rapidly, foresight, so that the bayonet may fit well. and fitted with a fast and loose pulley for disen- The barrels are now draw filed from end to end. gaging, &c, carries with it the triangularly-formed Gauges are next applied once more to every part,

studs of which, indeed, there are 12 of about 4 inches in length, and they strike the end of the hammer lever. It is needless to say that the hammer itself, therefore, rises and falls, rapidly, too, on the principle of the tilt hammer. In fact, at Enfield this hammer, with its die face-so to speak-falls upon the cone seat of a rifle barrel at the rate of 300 times per minute. Annealing is the next thing to be done, and it must be done carefully. The atmosphere must be jealously excluded, and charcoal used to prevent decarbonisation. Great care is necessary with regard to the degree of heat applied in annealing. The desideratum is to make the material "mild" and easy to work without deteriorating its strength or quality.

The succeeding process is that of rough boring. This, too, is accomplished at the Government works in a machine of American origin. The machine is so contrived as to bore four barrels at once. Perhaps a brief description of it may not be uninteresting. Four spindles, geared together, are driven by a pulley with a loose one beside it. These spindles rest horizontally on a frame supported by two standards, the frame also forming a trough, and holding an abundant supply of cold water for keeping the barrels cool whilst being bored. The boring "bits" resemble twisted augers, the cutting portions being about six inches in length, but welded to rods sufficiently long to pass completely through the barrel. The ends of these bits are secured into the sockets of the spindles, the barrels being fastened horizontally in the machine. A self-acting feed causes the bits when in motion to take a cut completely through the barrels. The operation is repeated, and then the barrels are taken out and straightened by blow of hammer. The outside of the barrel next claims attention, and it is turned in a peculiarly constructed self-acting slide lathe, with a copying bar attached to produce the required figure. The tool rest of this machine is so devised as to carry two cutters, one in front, the other opposite and behind. One of these is to "rough," whilst the other takes a light and smooth cut. In order to prevent chattering a very solid bearing is made to follow the cutters closely. The turning properly done, another boring becomes necessary -the all-important one. Now one barrel at a time only is operated upon, the machine being a horizontal one fitted with a bracket which fits the barrel on the outside. The "bits" used for this boring are square, the sides being carefully ground on a stone. It does seem strange that so simple an in strument-by the aid only of the truthful eye of

and the rifling must be performed.

The machines used at Enfield for cutting the three rifle grooves in each barrel are of Belgian manufacture, strange to say, most of them having come from Liège. To describe them without diagrams is difficult. Their beds resemble somewhat those of the ordinary slide-lathe. On each bed there is a slide working backwards and forwards, after the plan, almost, of a planing machine. This slide is provided with a pinion which gears into a rack, the end of which slides on a radial bar set at the required angle from the central line of the machine. As the slide is made to traverse slowly along the bed, the radial bar is made to advance or recede according to the direction in which the slide is going, and of course gives a gentle twist to the pinion which has the cutter bar attached. This latter requires some explanation. It is composed of a bar of steel passing clear through the barrel, and filling it. The end remotest from that fixed in the pinion of the slide has a kind of mortice cut in it, with an inclined plane acting against a similar one on the other. The incline on the cutter has the point of a fine threaded screw bearing against it. This screw is prevented from moving by a square rod into which it is fixed, and which slides through a disc at the extreme end of the machine. All the time the cutter is travelling, it leaves the screw, and, as a spiral spring now acts upon the end of the cutter opposite the inclined plane, the tendency must be to force it out, and make it wider at the breech-end to the extent mentioned in a former article of this Magazine (September 2nd). The cut commences at the muzzle, and the barrel is firmly clamped whilst the "rifling" is going on. At the breechend there is an arrangement for setting the barrel into proper position for cutting the grooves at equal distances from each other. Supposing the spiral grooves or rifles to be now cut in a barrel, the next operation will be to remove the slight "burr" which the cutter, however clean it may have cut, will have inevitably left in its progress from muzzle to breech. In order to accomplish this the barrel is placed so that it cannot turn round, though it may be moved laterally. A leaden "lap" made to revolve at a very rapid rate is now introduced, and the barrel is made to slide to and fro upon the lap. The effect is to remove every vestige of wire edge which the cutter may have left, and to polish the interior of the barrel like a mirror.

Released from this machine, the barrel is next taken to the proof-house, where possibly the explosion within it of a heavy charge of gun

powder, and the propulsion through it of a bullet, may reveal some defect which will condemn it. If, on the contrary, it stands this test, it is passed forward to the machine or revolving cutter, which "mills" the fore-sight into shape. A little hand labour-such as removing by aid of smooth files any trifling imperfections left by the various machines-is now performed, and then comes the task of fixing the all-important "back-sight." This must be most carefully done, for accuracy of range and aim depends on this. The V, which is the centre point of this sight, must range exactly with the centre of the fore-sight, and both be central with the centre of the axis of the bore of the barrel. Without attending scrupulously to these points, indeed, the whole of the previous labour might be deemed as thrown away. Presuming that all has been satisfactorily done, from the bending of the "skelp" to the attaching of the back-sight, and that inspectors have pronounced it very good, the barrel has next to be bronzed; and in order to effect this, the exterior is made, in the first instance, to become oxidised, by application of water, and then to pass through a simple chemical process. Polished over the bronzing, it is now fit for its walnut-wood bed, and for the companionship of those component parts which go to make up the handsome weapon with which the various and happily increasing number of rifle club members are becoming familiar, but which tilely. For much of the information in the forewe trust they may not be called upon to use hosgoing paper we are indebted to the courtesy of C. F. Hayes, Esq., of the Small Arms Factory,

Enfield.

INSTITUTION OF MECHANICAL
ENGINEERS.

THE Annual Meeting of this body was held in
Leeds, during last week, under the presidency of
Mr. John Penn, of Greenwich. The first meeting
was held in the Civil Court, at the Town Hall, on
Tuesday, Mr. Penn presiding.

FILE-CUTTING MACHINERY.

The first paper was a description of Bernot's file-cutting machine, by Mr. Thomas Greenwood, of the firm of Greenwood and Batley, machine makers, Leeds. Mr. Greenwood alluded to the fact that whilst machinery had been introduced into most manual operations, file-cutting remained stationary. Various machines had been invented in America and this country, and large sums of money had been spent by manufacturers in Sheffield, but partly from difficulties, real and imaginary, and also from the opposition of the operative file-cutters, these experiments had failed up to within a recent period. So great were the prejudices of the operative file-cutters that they refused to teach the apprentices how to grind their cutting chisels until the last year of their apprenticeship, and the tariff of prices remain fixed, on the supposition that no improvement had taken place in the rolling of steel, thus entirely ignoring the progress that had been made; and forgers charged the same price for drawing the tang upon a round or square rod of steel for a parallel or equalling file as they did for forging a half-round taper file of the same length. The actual process of file-cutting, however, was one of the simplest description. It consisted in driving a chisel of suitable form and inclination to a small depth into the prepared surface of the blank, and steadily withdrawing it again. The difficulties to be surmounted were to present the blank perfectly parallel to the cutting edge of the chisel; to withdraw the chisel from the incision made in the blank without damaging the edge of the newly-raised tooth; to prevent a rebound of the chisel after the blow which drove the chisel into the blank before the next blow was struck; to give a uniform traversing motion to the blank, ensuring regularity in the teeth; to proportion the intensity of the blow to the varying width of the file, so as to give a uniform depth of cut; and to perform these operations at such a speed as to make them commercially pro

fitable. In most of the attempts which had been made the idea had been to construct an iron arm and hand to hold the chisel, and an iron hammer to strike the blow, but the vibration which attended this mode caused irregularity in the work, and a ragged uneven edge on the tooth. The slow speed, too, at which these machines were worked rendered them unable to compete with hand labour. In the machine invented by M. Bernot, of Paris, these difficulties were obviated. The blow was given by the pressure of a flat steel spring pressing upon the top of a vertical slide, at the lower end of which the chisel is firmly fixed The slide was actuated by a cam, making about one thousand revolutions per minute, thus obviating the vibration consequent upon the blow with an iron-mounted hammer. After explaining the machine more minutely, by means of diagrams, Mr. Greenwood remarked, with regard to the durability of the cutting chisels, that it was found that they cut five times as many files as could be cut by hand, without re-sharpening. In the files cut by this machine the teeth were raised with perfect regularity, and, consequently, when

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THE MECHANICS' MAGAZINE.

[SEPTEMBER 16, 1859.

and

ferred which, combined with naturally good | We cannot give a description of the valve without positions for absorbing heat, offered the greatest diagrams, but we may state that the objects of the facility for circulation of the water. The paper invention are to carry off the steam as fast as it is concluded by remarking that great as had been generated above the pressure the boiler is intended the progress of late years in the construction of to work at; to be entirely out of the reach or consteam-engines, and the economical use of steam trol of any one to tamper with or overload it; by working expansively, this had not been accompanied by equal progress in the construction of getting low in the boiler, the valve shall blow off steam boilers; for, whatever might be the scienti- steam, and avoid the possibility of any explosion to be so arranged that in the event of the water fic knowledge in the latter branch of engineering, or injury beyond the burning of the plates if more it was certainly not favourably exhibited in the water be not supplied. generality of boilers in present use. trary, the laws of combustion and evaporation seemed generally to have been almost entirely On the conignored, and waste of fuel and rapid deterioration of boilers had been the natural consequences.— Mr. Kitson briefly alluded to the importance of the subject raised by Mr. Longridge, and said that the time had come when more attention ought to be paid to the construction of their been committed was, that persons purchasing boilers. One great mistake which had hitherto boilers simply fixed the power and the amount per ton, without reference to the construction. This

and the sitting terminated, the members proceed-
ing to visit Messrs. Marshall's flax-mill, and other
A vote of thanks was accorded to Mr. Naylor,
works thrown open to their inspection. In the
the Victoria Hall.
evening of Tuesday a conversazione was held in

Court on Wednesday.
The Second Meeting was held in the Civil
Mr. Penn again presided.

the Application of Super-heated Steam in Marine The first paper read by the Secretary was "On

SUPER HEATING OF STEAM.

the file was used, each tooth performed its proper had, commercially, been really a great error, be. Engines," by Mr. J. Penn, the President. The

4d.

share of work; whereas, in hand-cutting, from the varying power of the muscles, especially towards the close of the day, it was impossible to produce such perfectly uniform work. Every description of round or half-round files was cut by the use of a revolving bed, and dividing apparatus for round and hand round files. The paper concluded by stating that a manufactory employing twelve of these machines had been established at Douai, in the north of France, and another at Brussels. A machine, which had been fitted up in the room, was then put into operation by means of manual power, which, however, could not give the full velocity, but notwithstanding this the work done was of a very satisfactory character, the files cut being the full-sized flat hand files. A discussion ensued, and in reply to Mr. Fothergill, Mr. Cowper, and others, Mr. Greenwood said that the relative cost of cutting the files, as shown by practice at Douai, was as per dozen to 28. 8d. for manual labour, on a certain class of work, which left a large margin after the cost of the machine and power in favour of machine work. As to the durability of the files, it was decidedly greater than that of ordinary files. The difference of production was as ten to one, and the machine would last as long as ordinary complicated machinery. There was no difficulty in cutting round and half-round files. There was also an additional advantage in the equality of the work obtained. In hand labour it was found that the files made in the afternoon were not so good as those made in the morning, the muscles becoming relaxed, and the blow, therefore, less regular in force. It cut the taper files all one depth, but no doubt the pitch could be altered if necessary, by making the machine a little more complicated. On the suggestion of Mr. Maudslay, Mr. Greaves, who had charge of the machine, briefly addressed the meeting. He said that he had been engaged in file-cutting twenty-five years, and he was prepared to state that the machine would cut as good files as could be made by hand, if properly attended to. It was necessary, how ever, that the machine should be fixed, and not re-set every half-hour. thanked Mr. Greenwood for his paper, and the The President then discussion terminated.

ECONOMY AND DURABILITY OF STEAM-BOILERS.

The Secretary then read a paper by Mr. Long ridge, of Manchester, on the "Economy and Durability of some classes of Steam-boilers." The paper was of a very elaborate character, requiring a number of statistics and diagrams for its illus. tration. With respect to the best surfaces for heating, Mr. Longridge said there could be no question that horizontal surfaces were the best for absorbing heat, but unless this heat were carried off, and accumulation prevented, the prac tical value of such surface for generating steam would be much impaired, and the plates speedily injured. Hence those surfaces were to be pre

maker, and a higher degree of intelligence
brought to bear on the construction of boilers, the
cause if greater power were given to the boiler-
result would be to the benefit of the purchaser.
After some remarks from Mr. Goodfellow, of Man-
chester, with respect to evaporation, the President
and Mr. Bastow made a few observations, and the
passed to Mr. Longridge.
discussion closed.—A vote of thanks was then

MORRISON'S DIRECT-ACTING STEAM CRANE.

by Mr. Morrison, of Newcastle-on-Tyne, descriptive of a direct-acting steam crane invented by The secretary then read an interesting paper that gentleman. For the usual complications of ordinary steam cranes, there was in this crane substituted a piston with a flexible piston-rod, working steam-tight through a stuffing-box in the top of the crane-post, passing over two pulleys, and forming the chain. By this arrangement the different movements of the crane were performed ing being performed by the admission of the with the greatest facility and precision, the liftlinder or crane post to a distance equal to the lift required. It would lift 32 feet, swing round, steam above, the piston forcing it down the cydischarge, and swing back to re-load, three times per minute. In other words, it would discharge three tubs of coal, of 2 tons each, in one minute.

Comparing it with water, taking the latter at a
pressure of 60 lbs. per square inch, and steam at
50 lbs., the writer said he had found that the cost
would be 8d. The cost of a machine with boiler
of steam was but 44d. per hour, whilst water
discussion took place with respect to the relative
and steam-pump would be about 4601.-Some
cost of hydraulic and steam cranes, after which a
vote of thanks was passed to Mr. Morrison.

ALLAN'S NEW PRESSURE GAUGE.
by Mr. Alexander Allan, on a new pressure gauge,
The next paper read by the Secretary was one
invented by him.
consisted in indicating pressure, either above or
below that of the atmosphere, by the more or less
The principle of the gauge
compressed or expanded condition of a measured
quantity of air contained within the gauge, This
was acted upon by the pressure through water or
other fluid contained within a bent pipe, which
other to the boiler or vessel containing the pres-
was attached at one end to the gauge, and at the
water, as seen in a glass tube attached to the body
of the gauge, indicated the extent of the pressure,
The surface line of the
pressed their favourable opinion of this gauge,
on a graduated scale.-Several gentlemen ex-
one of which was exhibited, and a vote of thanks
was passed to Mr. Allan for his paper.

sure to be indicated.

HASTE'S SAFETY-VALVE.

Naylor, of London, descriptive of Haste's safety-
The last paper read was one by Mr. William
valve for steam-boilers, which was illustrated by
a section of the valye, and a number of diagrams.

paper was of a technical character, but of great interest to practical men. supplied to steam-engines had long existed, and it The writer stated that an opinion in favour of super-heating the steam might be obtained from this principle, though until had been maintained that important advantages recently but little had been effected in its practical application. Super-heated steam seemed to have been first definitely tried by Mr. Thomas Howard, test the experiment properly (though it established of Rotherhithe, about twenty-seven years ago. the principle), and it was given up. Soon aftermachine was too delicate in its construction to Considerable economy was effected, but the wards Dr. Haycroft, of Greenwich, took up the subject, and was convinced of its advantages. The importance of the principle was first impressed upon the writer many years ago, and he became satisfied, from the results of experiment and observation, that great advantages in economy of fuel might be obtained, the main question to be tical objection from complication of apparatus, settled being whether it involved any serious praclubrication of the engine. Recent trials, made on risk of derangement and failure, or difficulty in clusions:-That an advantage can be obtained from the use of super-heated steam, amounting to a large scale, led the writer to the following conheating enables all the important advantages of an economy of fuel of from 20 to 30 per cent. in marine engines; that a moderate extent of superthe plan to be obtained; and that apparently from extra wear and tear, risk of failure, complinothing objectionable is then necessarily involved The real advantage in employing super-heating cation of apparatus, or difficulty in lubrication. steam appeared to be in preventing the presence of any water in the cylinder of the engine, and ensuring that it should be occupied always by engine, instead of one working with a mixture of nothing but pure steam; making it a real steamdenser during half the time of each revolution of the crank, was exposed during that time to the. interior of the cylinder, being open to the conwater and steam. In all condensing engines the low temperature of the condenser, or about 125 degrees, with a vacuum of 134 lbs. per inch below the cylinder, thus cooling down the whole mass tion of heat from both the sides and the end of the atmosphere, or 27 inches of mercury. was, consequently, a rapid absorption and radiain the next stroke, at a temperature of 260 deg. if at 20 lbs. per inch above the atmosphere, of metal. The steam admitted into the cylinder heated them up again, being robbed thereby of a coming in contact with these cooled surfaces, portion of its heat; and the consequence was the deposit of a quantity of water in the cylinder, from metal of the cylinder. A portion of this water in tionate to the quantity of heat imparted to the the condensation of an amount of steam proporthe cylinder might be evaporated again into steam towards the end of the stroke, by carrying the

There

expansion of the steam down to a sufficiently low |
pressure: but even then its effective value as steam
in propelling the piston would have been lost
during all the previous position of the stroke.
Now, if as much heat be added to the steam, by
super-heating it before entering the cylinder, as
would supply the amount of which it was robbed
by the cylinder, it would remain perfectly dry
steam throughout its stroke, and not a drop of
water would be deposited. This, the writer
believed, was the mode in which the super-heating
of steam acted in producing a saving of steam,
and consequent economy of fuel, by preventing
the extensive loss or waste of steam that ordi-
narily took plate. The addition of 100 degs. of
heat to the temperature of the steam insured the
accomplishment of the desired object with steam
at 20 lbs. per inch, as used in marine engines.
The writer then proceeded into more technical
details, reference being frequently made to the
diagrams, and said, that having fitted the engines
of the Peninsular and Oriental Company's steamer
Valetta with super-heating apparatus (illustrated
by diagrams), the experiments made gave a sav-
ing of 20 per cent. of fuel. These experiments
were not complete, but they were entirely satis-
factory as far as they went.-A very interesting
though technical discussion ensued, in which Mr.
W. S. Ward, Mr. Morrison, Mr. Cowper, Mr.
Maudslay, the President, and other gentlemen,
took part; after which a vote of thanks was
passed to the President for his paper.
SUPPLYING LOCOMOTIVE TENDERS WITH WATER.
The Secretary read: a Description of Fryer's
Apparatus for Supplying Locomotive Tenders
with water," by Mr. James Fenton, of Low Moor.
By this apparatus it is proposed to force water
from tanks below the level of the lines into the
tenders, by means of the pressure of condensed
steam from the engines; and it was stated that
the experiments tried in a large sugar manufactory
at Manchester had been highly successful. The
great value of the apparatus was where water
could only be obtained at low levels, and it was
said that there was greater protection from frost,
the water being stored below the level of the
ground. After a short discussion, in which Mr.
Fryer explained the apparatus in a more popular
manner, a vote of thanks was passed to Mr.
Fenton for his paper, and to Mr. Fryer for his
communication;

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IMPROVED RAILWAY BREAK.

The next paper read was by Mr. Alex. Allan, "On Increased Railway Break Power for Stopping Railway Trains." After referring to the importance of increasing the break power for stopping fast trains within a shorter distance than at present, the writer said that the subject of the paper was a plan for obtaining increased break power, by retarding the speed of the engine, by means of a throttle valve, placed in the exhaust pipe, which could be instantly closed to any required extent, so as to obstruct the exit of the steam from the cylinders, the regulator remaining open, at the same time that the exhaust steam was admitted to a small cylinder, the piston of which acted through levers on a break on the engine wheels. The break cylinder applied the breaks simultaneously to the leading and trailing wheels of the engine, and the driving wheels were at the same time retarded by the back pressure of the exhaust steam on the pistons, consequent upon the closing of the throttle valve in the exhaust pipe. The power of the break cylinder was limited, so as not to skid the wheels, in order to avoid

A

der, and 11 empty carriages, weighing 85 tons,
and going at a speed of 36 miles per hour, was
stopped in 23 seconds, running 220 yards. In re-
ply to an inquiry, Mr. Allan said the application
of the break was so regulated as to prevent any
shock.

STEAM CRANE.

The Secretary next read "A Description of a Steam Crane," by Mr. J. C. Evans, of London, which gave rise to some remarks by Mr. Maud slay, the President, and others, after which the President thanked Mr. Evans for his paper.

THE PUMPING-ENGINES AT ARTHINGTON.

ON THE EARTIP'S INTERNAL TEMPERA-
TURE, AND THE THICKNESS OF ITS
SOLID CRUST.

By WILLIAM HOPKINS, Esq., M.A., LL.D., F.R.S.
If we descend beneath the surface of the earth,
and observe the temperature at different depths,
it is found that within a depth ranging from 50
to 80 feet, the temperature changes periodically,
being affected to that depth by the heat which

the earth receives from the sun at different seasons of the year. The annual variation, however, becomes less as the depth increases, till at the depth above-mentioned it becomes insensible. The proceedings of the sitting were closed by a At greater depths, the temperature is invariable description of the pumping-engines at Arthington at each point, but increases with the depth, at the Water-works, communicated through the Secre- rate on an average of 1° (F.) for a depth of tary, but it contained no facts which have not between 60 and 70 feet. The best observations already been made public.-Mr. Anderson then which have been made on this subject are those moved a vote of thanks to the President for his in deep mining shafts and deep artesian wells; conduct in the chair, which was seconded by Mr. the greater depth the more completely do anoFothergill, and carried by acclamation. At the malous influences counterbalance each other. The close of the meeting the following objects of in-greatest depths at which such observations have terest were exhibited for the inspection of the been made in Western Europe, are at Monkwearmembers:-A steam carriage for common roads mouth and Dukinfield, in this country; the Puit at the works of Messrs. Witham, Kirkstall-road; de Grenelle, at Paris; Mondorff, in the Duchy Naylor's steam-hammer, Kirkstall Forge; two of Luxembourg; New Seltswerk, in Westphalia; locomotive engines, with welded boilers, at the and at Geneva. At the first two places the Midland Station; Aytoun's safety miners' cage, observations were made in vertical shafts of coal in a yard opposite to the Town Hall; roof and mines; the depth of the one at Monkwearmouth large bell of the Town Hall; Hattersley's type- being upwards of 1,800 feet, and that at Dunkincomposing machine, in the Victoria Hall; and Mr. field upwards of 2,000 feet; and in both cases the James's machine for winding up clock weights, in observations were made while the workmen were the entrance to the Victoria Hall. The Members sinking the shafts, and with every precaution were taken by special train to the pumping-works against the influence of any extraneous causes at Arthington, after which they dined together in which might affect the observations. The former the Wellington Hall. On Thursday they visited gave an increase of 1° (F.) for every 60 feet of Low Moor and Saltaire. depth, the latter for about every 72 or 73 feet. The sinking of the Puit de Grenelle was superintended by Arago. The mean increase of temperature was 1° for every 60 feet. At Mondorff the bore was 2,400, being that of an artesian well; the increase was 1° for 57 feet. At New Seltzwerk the artesian well, penetrating to the depth of 2,100 feet, giving an increase of 1° (F.) for 55 feet. The average of these is very nearly 1° for 60 feet. Numerous other observations are confirmatory of those results, though observations at smaller depths present many anomalies indicating the operation of local causes.

THE BRITISH ASSOCIATION.

ABERDEEN, WEDNESDAY, Sept. 14.

THE meeting of the British Association for
1859 commenced this evening in the new Music-
great interest attached to the meeting in conse-
hall. There was a very large attendance, and
quence of his Royal Highness the Prince Consort
being the president elect.

Professor Owen, on retiring from the chair,
congratulated the members on the prosperous con-
dition of the Association, and that it was presided
over by his Royal Highness.

delivered a very able address, which occupied 40
The Prince Consort, after taking the chair,
minutes in delivery, and was loudly applauded
throughout.

Sir Benjamin Brodie moved, and the Lord Pro-
vost of Aberdeen seconded, a vote of thanks to his
Royal Highness, which was enthusiastically
passed by the large audience.

FLEET-STREET, THURSDAY AFTERNOON, Sept. 15.
We confidently expected to receive a report of
the Prince Consort's speech from our correspon-
dent in Aberdeen, in time for publication in this
number; but it has not yet reached us, and as we
have to publish at noon to-morrow, it is not
possible to delay our Magazine further for it.

LIST OF NEW BOOKS.
Brown's Companion to the New Rifle Musket, 2nd edit.,
2s. 6d.

Burnett's Tillage a Substitute for Manure, 5s.
English Cyclopædia, Knight's Arts and Sciences, Vol. II.,

128.

Grantham on Iron-ship Building, with vol. of Plates, 2nd.
ed., 25s.

Laurie's Tables of Simple Interest from 2 to 5 per cent.,
24 edit., 21s.
Moor's The Ventilation of Mines, 5s.

Schools, 4s. Gd.

If a sphere of very large dimensions, like the earth, were heated in any degree and in any manner, and were left to cool in surrounding space, it is shown, by accurate investigation, that after a sufficient and very great length of time, the law according to which the temperature would increase in descending beneath the earth's surface, within depths small compared with the earth's radius, would be-that the increase of temperature would be proportional to the increase of depth. This coincides with the observed law, if we neglect the anomalous irregular variations which are found to exist more or less in each locality. Now according to this law, the temperature at the depth of 60 or 70 miles would probably be sufficient to reduce to a state of fusion nearly all the materials which constitute the earth's external solid envelope; and hence it has been concluded, that the earth probably consists of a central molten mass as a fluid nucleus, and an external solid shell, of not more than 60 or 70 miles in thickness: and some geologists, desirous of rendering the conclusion the foundation of certain theories, have considered the thickness even less than that now mentioned.

This conclusion, however, rests on reasoning in which an important element is wanting. It involves the hypothesis that the conductive power of the rocks which constitute the lower portions of the earth's crust, is the same as that of the rocks which form its upper portion. This conductive power of any substance measures the

wearing flat places on the tyres, and to produce Todhunter's Spherical Trigonometry for Colleges and facility with which heat is transmitted through the greatest effect in retarding the speed. break power of from 14 to 22 tons could thus be obtained by the steam break alone. The retarding power of this steam break had been tried on the Scottish Central Railway with the most satisfactory results. A train consisting of engine, ten

THE GREAT EASTERN-Erratum.-For the correction of an error in our last week's article on this ship, see the first paragraph of our Gossip" of this week.

66

it; and it is easily proved, by accurate investigation, that when the same quantity of heat passes through superimposed strata of different conduc* Authorised abstract of a recent lecture at the Royal Institution,

tive powers, the increase of depth corresponding to a given increase of temperature (as 1°), is in any stratum proportional to the conductive power. Consequently, if the conductive power of the lower portions of the earth's solid crust be greater than that of the thin upper portion of it through which man has been able to penetrate, the depth to which we must proceed to arrive at a certain temperature (as that of fusion for the lower rocks) will be proportionally greater. The precise nature of the rocks situated at a great depth can only be judged of by analogy with those which are accessible to us; but those geologists who adopt the conclusion of the extreme thinness of the earth's crust, will doubtless admit that its inferior part must be of igneous origin, and must therefore be allowed to bear a certain resemblance to igneous rocks on the surface of the earth. Mr. Hopkins had recently made a great number of experiments on the conductive powers of various rocks. That of the softer sedimentary rocks, which are great absorbents of water, is very much increased by the quantity of moisture they contain; but taking chalk, one of the best absorbents, its conductive

the pole of the ecliptic with a radius of nearly
233, equal to the inclination of the equator to
the ecliptic, or the obliquity. The whole of this
revolution is completed in about 25,000 years;
but, as follows from what has just been stated,
without any change, beyond small periodical ones,
in the obliquity. A corresponding change of
position must manifestly take place also in the
position of the equinoxes, which have thus a mo-
tion along the ecliptic in a direction opposite to
that in which the signs of the zodiac are reckoned,
completing a revolution in the period above men-
tioned of 25,000 years. It is called the precession
of the equinoxes.

This precessional motion has been completely
accounted for under the hypothesis of the earth's
entire solidity, and that of a certain law according
to which the earth's density increases in approach-
ing its centre; but some years ago Mr. Hopkins
investigated the problem with the view of ascer-
taining how far the observed amount of precession
might be consistent with the existence of a fluid
nucleus. The result was, that such could only be
the case provided the thickness of the solid shell
were much greater than that which, as above

power, even when saturated, is not half so stated, has been supposed by many geologists.
great as that of some of the igneous rocks The numerical result was, that the least admissible
on which Mr. Hopkins had experimented. Cal-thickness of the crust must be about one-fifth of
careous, argillaceous, and siliceous substances re-
duced to fine powder, stand, with reference
to their conductive powers, in the order in
which they are now mentioned, the conductivity
of the first being the least; and when in a com-
pact state, all that contributes to give a hard and
erystalline character to the substance, and con-
tinuity to the mass through which the heat is con-
ducted, increases the conductive power. These
considerations lead to the conclusion that the con-

ductivity of the inferior portions of the earth's solid crust must be much greater, and may be very much greater, than that of the less consolidated and mere superficial sedimentary beds. Moreover, the temperature of fusion of certain substances, as Mr. Hopkins had shown by experiment, is much increased by great pressure; and by analogy it may be concluded, that such would, at least in some considerable degree, be the case with the mineral matter of the earth's crust. The chalk is that formation in which the most nu

merous and some of the best observations on terrestrial temperatures have been made, and it would seem impossible to conclude from actual experiment and the considerations above stated, that its conductive power can exceed one-third of that of the inferior rocks, and may not improbably be a considerably smaller fraction of it. Now the increase of depth in the chalk corresponding to an increase of 1° (F.) is well ascertained to be very nearly 60 feet, and therefore the rate of increase in the inferior rocks must probably be at least three times as great as in the chalk, and may be very considerably greater still. Hence, supposing that the thickness of the solid crust would be about 60 miles, if the conductive power of its lower portion were equal to that of chalk, its actual thickness must probably be at least about 200 miles, and may be considerably greater, even if we admit no other source of terrestrial heat than the central heat here contemplated.

There is also another way of investigating the thickness of the earth's crust, assuming the whole terrestrial mass to consist of a fluid nucleus, inclosed in a solid envelope. If the earth were accurately spherical, instead of being spheroidal, its axis of rotation would always remain exactly parallel to itself, on the same principle as that on which the gyroscope preserves, in whatever position it may be held, the parallelism of the axis about which it rotates. But the attraction of the sun and moon on the protuberant equatorial portions of the earth's mass causes a progressive change in the position of the earth's axis, by virtue of which the North Pole, or that point in the heavens to which the northern extremity of the earth's axis is directed, instead of being stationary, describes a circle on the surface of the heavenly sphere about a fixed point in it called

the earth's radius; but without assigning any
great importance to an exact numerical result,
Mr. Hopkins had a full confidence in the investi-
gation, as showing that the thickness of the crust
could not be so small as 200 or 300 miles, and
consequently that no geological theory can be ad-
mitted which rests on the hypothesis of the crust
being nearly as thin as it has been frequently
assumed to be.

thickness? (and this is the only question of geological importance)-Mr. Hopkins denied the validity of either of the objections above stated.

Thus, both the modes of investigation which had been described lead to like conclusions respecting the least thickness which can be assigned to the solid envelope of our globe. It must be much greater than geologists have frequently imagined it to be.

year.

THE NEW CALCUTTA MINT. THE machinery for the new Calcutta Mint is rapidly approaching completion, and will be shipped for that place before the end of the We have no hesitation in saying, after a personal examination of the drawings for the building, and of the various mechanical appliances prepared, or in course of preparation by James Watt and Co., for the establishment, that this new money factory will, when completed, be the most extensive and perfect in the world. The designers of it, it is true, have had the advantage of inspecting all existing mints, and thus the opportunity of improving upon them. They have used that advantage with extraordinary effect, however, and have left apparently little for others to improve upon.

The space of ground upon which the machinery, on reaching India, will be erected is large, and the workshops and offices are in course of rapid construction. Two steam-engines of (we believe) fifty horse-power are intended to give motion to eighteen rolling mills of various sizes, for the breaking down and laminating of silver and gold bars. The rollers of these mills are of chilled cast

remarkable work will obtain further attention at our hands, illustrative as it is of mechanical improvement and the march of civilization.

The influence of the interior fluidity on the iron, the largest being 18 inches in diameter, and precessional motion above described, is due to the the smallest 10 inches. There will be eight cuttingdifference between the motions which the attrac-out presses of great productive power, from the tions of the sun and moon tend to produce on a peculiarity of their make, and the rate at which solid mass in one case, and a fluid mass on the they will work. What is called the drawbench other. It has been recently stated, as an objec- will not, as in the British Mint, be used. It is tion to this investigation, that the interior fluid considered that well-finished rolls carefully atmass of the earth may move in the same manner tended to, will produce work as accurate as that as if it were solid. The only reply which could which is turned out by this expensive appliance, be given to such an objection was, Mr. Hopkins and we have little doubt of the fact. Twelve conceived, that it was mechanically impossible coining-presses, made to vibrate at the rate of that these motions should be the same, though 200 strokes per minute, and to produce coins as the resulting precessional motion for the solid rapidly, it is said, complete the fitments of this crust, under certain conditions, to be determined mammoth Mint. The presses are to be impelled only by the complete mathematical solution of by compressed air acting upon pistons attached to the problem, might be the same as if the whole their fly-arms, and working in iron tubes concenmass were solid. The effect of the attractions of tric with the vertical screw-pin to which the die the sun and moon also depends on the ellipticity is attached-an arrangement altogether new in of the inner surface of the solid shell; and it has money-making machinery, and now, therefore, to been said that since that ellipticity depends on the be put on its trial, except as experimentally at law of the earth's density, which can only be Soho for the first time. At a further period this imperfectly known, no result can be depended on which involves that ellipticity. This was not a correct statement of the problem. It was assumed in the solution referred to, that the ellipticity of the inner surface would depend partly on the law of density, and partly on the forms of the isothermal surfaces. Mr. Hopkins had supposed it possible, at the time he was engaged in this investigation, that a surface of equal solidity might approximate to a surface of equal pressure; he has now experimental reasons for believing that it must approximate much more nearly to an internal surface of equal temperature. Now, for depths greater, probably much greater, than those which have often been supposed to correspond to the thickness of the earth's solid crust, there is no doubt that the internal isothermal surfaces have a greater ellipticity than the external surface itself-a conclusion which is independent of the law of density. Hence, a like conclusion will hold with reference to the internal surface of the shell, if it approxi mate sufficiently to the surface, of equal temperature; and this is the conclusion most unfavourable to the thin shell supposed by some geologists. Restricting the interpretation, then, of Mr. Hopkins's results to the question, whether the earth's solid shell be as thin as some geologists have supposed, or at least several hundred miles in

THE GREAT EASTERN. TO THE EDITORS OF THE "MECHANICS' MAGAZINE.' GENTLEMEN,-Will you permit me through the medium of your excellent Magazine to put the following question to those gentlemen who are so very confident as to the perfect safety of the Great Eastern, viz., what will be the effect of and upon that noble vessel when her monster engines are suddenly and severally released from all resistance by the paddle-wheels and screw becoming alternately out of water, as must be the case when she is resting upon and running directly across and through the crests of water of more than 40 feet altitude, or rather, of 80 or 90 feet, including the depth of the trough of the sea between them? W. II. JAMES, C.E.

September 6th, 1859.

SPILL'S NEW MILL-BANDING. Numerous readers having written to us for the address of the manufacturers of the new mill-banding described at page 152 of our Magazine for September 2, it may save trouble if we mention the address here; it is, we believe, Messrs. G. Spill and Co., 18 Bread-street, Cheapside, London, E.C.

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