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as the temperature increases. At last a point will be reached at which the whole of the water in globe a will be converted into steam, and at this point the mercury column will rise at a and sink at b; this is the saturation test, and the cause of its action will be easily seen. So long as vaporization went on in both A and B, and the temperature was maintained uniform, each globe would contain steam of the same pressure, and the columns of mercury, a and b, would remain at the same level. But so soon as the water in a had vaporized, and the steam began to superheat, the pressure in a would cease to remain uniform with the pressure in B, and the mercury column would at once fall, and thus indicate the difference. The instantaneous change of the position of the mercury is the indication of the point at which the temperature in the bath corresponds with the saturation point of the steam in a.

To show the delicacy of this test, I may instance that at 290° Fahrenheit, the mercury column would rise nearly two inches for every degree of temperature above the saturation point, as the increase of pressure arising from vaporization is twelve times that arising from expansion in superheating at that point, and a similar difference exists at other temperatures.

The apparatus, as employed for experiment, varies according to the pressure and other cir. cumstances of its use. Fig. 2 represents one of the arrangements which has been employed with suc

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cess.

KER'S

ENT STREET CHAN

It consists of a glass globe of about seventy cubic inches capacity, in which is placed, after a Torricellian vacuum has been formed, the weighed globule of water. The globe with the stem is shown at A; this is surrounded by a copper boiler B B, prolonged by a stout glass tube CC, enclosing the globe stem. This copper boiler forms the water and steam bath through which the globe is heated, and in fact corresponds to the second globe B, in the former figure. The fluctuating mercury column, or saturation gauge, is placed at the bottom of the tube CC, and the saturation point is indicated by the rise of the inner mercury column a, and the fall at the same time of the outer mercury column b. As soon as the whole of the water in the globe 4 is evapo. rated, there is an instantaneous rise of the inner mercury column to restore the balance of pressure, and that progressively with the rise of temperature.

As an auxiliary apparatus the boiler is provided with gas-jets, E, to heat it, and with an open oilbath G to retain the glass tubes at the same temperature as the boiler, and this oil bath is placed on a sand bath, and also heated with gas. A thermometer D registers the temperature, and a pressure gauge Fthe pressure of the steam; and a blow-off cock H serves to reduce the temperature when necessary. A number of results have already been obtained, but they are not yet sufficiently advanced to be made public. The following numbers have been, however, approximately reduced from the theoretical formula above, and the experimental results may illustrate the use of this method of research. The most convenient way of expressing the density of steam is by stating the number of volumes into which the water of which it is composed has expanded. Thus one cubic inch of water expands into 1,670 cubic inches of steam at 212° Fah., into 882 cubic inches at 251°, and into 400 cubic inches at 304°, and so on; in this way the following numbers have been computed:

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540

604 490

283° These determinations at pressures varying from ten to fifty lbs. above the atmosphere, are not accurate reductions from the experimental results, but only approximations. But they uniformly show a decided deviation from the law for perfect gases, and in the direction anticipated by Professor Thomson, the density being uniformly greater than that indicated by the formula. I hope by the time of the next meeting of the Association, with the assistance of my friend Mr. Tate, to be enabled to lay before the section a series of results which will fully determine the value of superheated steam, and its density and volume as compared with pressure at all pressures, varying from that of the atmosphere to 500 lbs. on the square inch.

WALKER'S PATENT FRICTIONLESS STEAM BOILER FLOAT. SIMPLICITY of arrangement is of vital importance in all boiler fittings. The lives of so many depend upon them that we receive all real improvements in their construction as matters of considerable importance. The old stone float, with its counterbalance weight, its suspension rod, gland, and steam-tight packing, the friction of which materially impairs the certainty of its action, is for this reason a doubtful indicator, and should never be used in its old form without the boiler to which it is fitted having an adjunct in the shape of a glass gauge. Were it not, however, for this objection of friction the float in question would be all that we could desire as an indicator. Mr. Walker, of Birmingham, has in a very simple manner overcome the difficulty, and produced a remarkably sensitive float. It has now been in action some time, and has never been known to fail, so that we have confidence in laying it before our readers as a practically good thing.

Walker's patent frictionless float consists of a lever enclosed in a cast-iron box made in the form of a segment of a circle. The end of the lever on which it vibrates is fitted with a spindle, which passes through one side of the box, and carries on its outside end another lever extending in a line with the inside one as a pointer, and the other way to receive a weight to balance the float. T the vibrating end of the lever situated inside the box is attached a copper chain, which passes down a pipe bolted to the top surface of the boiler, and forming a standard to the segmental box; to the lower end of this chain is suspended the float of ordinary form. The chain is also carried up from the internal lever to a brass plug, which forms a valve at the lower end of a whistle situated at the top of the segment. When the water is the right height in the boiler the chain hangs loose, but if it falls too low the tension pulls down the plug or valve, which is held by a spring in its place, and an alarm is sounded. On referring to the engraving of the sectional elevation, the various parts will be seen in position; A shows the segmental box, B the internal lever, C the chain leading to float, D chain leading up to whistle valve, E the whistle and valve, Fthe external lever and balance weight, with the external pointer in a line with the internal lever.

By the side of this section is an end elevation, which completes the delineation.

Arrangements for the reception of the Great Eastern, which is expected to arrive at Southampton from Holyhead early next week, are in active progress. As stated in the Times of this morning, the moorings will be furnished from Portsmouth dockyard by Admiralty order, and they will be laid down off Fawley beacon, about four miles down the Southamp ton Water, where the great ship will have plenty of room to swing freely at all times of tide. The anchors, blocks, chains, pendants, and bridles to form the moorings for the great ship in Southampton Water, were yesterday selected in Portsmouth Dockyard, and lighter for conveyance round.-The Times, Thursday. will this morning be shipped on board a Government

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TYSSEN'S APPARATUS FOR INDICATING
THE SPEED OF SHIPS.

ship has run one knot. The shaft k also carries a
pinion n, which gears into a wheel o on a shaft
supported by a bracket p screwed to the front
plated. This shaft carries a pointer that revolves
round a dial plate q, and indicates when the ship
has run from one to ten knots. The shaft which
carries the wheel o also carries a pinion that
gears into a wheel containing the same number of
teeth as the wheel o. The shaft which carries
this wheels is supported by a bracket screwed to
the front plate A, and carries a pointer u that
revolves round a dial plate v, and indicates from
ten knots to a hundred the distance the vessel has
run; w is a tube for the passage of oil to lubricate
the spindle a. The patentee has shown the appa-
ratus to indicate up to a hundred knots the dis-
tance a ship has run, but without departing from
the invention the apparatus can be arranged to
show any other number.

wise have fulfilled the design, the surge from every form of paddle steam-boat was no doubt the fatal barrier to their adoption. When, at a later period the screw was adopted as a propeller, this seemed to meet the difficulties of the case, and screw-propelled boats have to some extent been adopted and are now in use: but even the screw has been found only applicable to the few canals which are of considerable depth; and in these the danger always exists of a disturbance producing a disintegrating effect on the sides and bottom of the canal, and where, as in the majority of canals, the depth does not exceed three to four feet, the working of the screw is found to be altogether impracticable.

MR. JACOBUS TYSSEN, of Rotterdam, in the kingdom of Holland, mariner, has just patented in this country an "An Improved Apparatus for Indicating the speed of Ships and other Vessels." He fits inboard on the axis of a three-bladed screw which is placed outside the vessel a wheel which gears into one or more wheels, and causes the last in the train to make, say, one revolution when the vessel is progressing at the rate of ten knots an hour, which revolution is shown upon an indicating dial. He does not confine himself to wheels made to work and show this speed only, the invention consisting in indicating by means of registering wheels placed inboard, the revolutions of a screw working in the water fitted on the axis of the first wheel in the train, the train of wheels being set to show so many knots per hour on the indicator according to the revolutions of the screw in the water. Fig. 1 of the accompanying engravings is an exterior front elevation of an apparatus for indicating the speed of ships and other Vessels constructed according to this invention; Fig. 2 is a view with the front plate removed; and Fig. 3 is a side elevation of the apparatus with the exterior case removed. A B are two metal plates held together by rods C C C secured to the front plate by washers and screws as shown. The plates A B, with the mechanism they hold between them, and about to be described, are placed in an outer case D, which is suspended by a lug E to the side of a ship's cabin, or the stern of a vessel, on deck, or in any other convenient position. a is the main spindle, from which the whole motion is derived; the outer end of this spindle carries a link and eye to which a line is attached, which line carries at its extremity a three-bladed screw, a view of which is given at Fig. 4, but the patentee does not limit himself to this form of the failure of most of these efforts is apparent, the same speed. This, I think, must be an exag

blade. As the vessel moves through the water, this screw revolves, which through the line attached to it gives motion to the spindle a, and this through wheels and pinions indicates on a dial or dials the speed at which the ship is travelling, as is about to be explained. The spindle a carries a pinion b, which gears into a wheel c, supported by a bracket d screwed to the back

ROBERTSON PATENT CHAIN-PROPELLER.

By Mr. PETER SPENCE.

AT the request of the patentee and several gentle-
men engaged in bringing this invention into
practical operation, I have undertaken to give a
short description of it to the mechanical section
of the British Association.

As mechanics is a department with which either
theoretically or practically I am only very
slightly acquainted, I hope the members of this
section will look charitably on my efforts if I
fail in giving a lucid description of what seems to
be an invention displaying considerable ingenuity,
and of great practical importance.

It is well known that great efforts have been
made to adapt steam power to the conveyance of
both passengers and goods on canals, but although

from the fact that on a very few canals is it at
this moment employed, yet there seems no reason
to doubt that if steam power can be made to suit
itself to the peculiarities of canal navigation, it
will be found, as in every other department of
agent.
mechanics, the cheapest and most convenient

In 1831, when the first efforts seem to have

The invention of Mr. Robertson fully meets and obviates these difficulties arising from the use of both the paddle and the screw, while it possesses advantages in obtaining the full effect of the power applied, which are apparent at once. In whatever mode power is applied to the propulsion of vessels in water, by the paddle or screw, there is a great loss of power, only a part being productive and the remainder wasted. For example, when the paddle is just entering the water on the one side, and leaving or emerging from it on the other, the powers expended in these actions only neutralise each other, and contribute nothing to the propelling of the vessel. So great is the loss of power in some circumstances, that one authority gives the following example: suppose a boat propelled in a stream, the power being affixed or applied to a cylinder, on which a rope is wound, the other end of the rope being attached to a fixed point at some distance up the stream or on shore, and that the power is afterwards applied by paddles in the stream; it will, he says, take three times the motive power in the latter case that it does in the former to propel the vessel at gerated estimate; but it clearly proves the great loss of power in certain cases, and the probability that it is considerable in all.

The peculiar principle of Mr. Robertson's invention is, that he applies the power by dragging the vessel from a fixed point, and its great ingenuity is, that the fixed point is at the same time a moveable one, a constantly fixed point in relation

plate B. The shaft that carries the wheel e also been made to employ steam power on canals, Mr. to the power exerted by the engine in propelling carries a pinion e, which gears into a wheelf con- Fairbairn, who then engaged in an extensive the vessel, and a constantly changing point in

taining the same number of teeth as the wheel c.
This wheel ƒ is supported by a bracket g, and the series of experiments by which much valuable
shaft which carries the wheel ƒ also carries a pinion data was elicited, recommended for this purpose a
A that gears into a wheel i on a shaft k, which carries peculiar form of steam-boats with paddles in the
a pointer / that revolves round a dial plate m, which stern; but however well these boats might other-

when it has made one revolution shows that the

British Association, 1859.

relation to the course on which the vessel is being propelled. The construction of the propelling apparatus is as follows:-At or near the bows of a boat, say 70 feet long, is placed a steamengine, the main shaft of which crosses the bows of the vessel at or about the level of the deck; a

fixed pulley is attached to each end of this shaft, these pulleys projecting over the sides of the ves

THE MECHANICS' MAGAZINE.

THE DEEP-SEA PRESSURE GAUGE.
By HENRY JOHNSON Esq.*

sel; they are three feet or more in diameter, and THE few experiments which I have made on the pressure, and has not been strengthened for the

on their periphery have a hollow or groove to receive the chains which are to run over them; they are also so constructed as to take a firm hold

compressibility of water by pressure, show a
greater than indicated by Mr. Carston of 1 in
21,740 for the pressure of one atmosphere. The

[OCTOBER 28, 1859. without the support of the external pressure of the sea water, which would balance the internal present experiment, this experiment must be considered not as an exact experiment, but simply as an illustration of a principle; the amount of co:nprevious experiments.

of the chains as the power is exerted in dragging method adopted is that of subjecting to the pression being greater than that indicated by the

pressure of a column of mercury a bulb of water
on the short end of an inverted glass syphon, con-

The vessel is made of cylindrical form in order to allow some length for the piston and scale, and The

the chains over the pulleys. On the other or the
stern end of the boat are two pulleys, also pro-
jected over, one on each side; these are loose, so
that the chains merely run over them. Friction
rollers are also placed along each side of the ves-
sel, to carry the chains as they pass from the
stern to the bows of the vessel; the chains, which
are endless, pass or are dragged over fixed pulleys
at the bow of the vessel, and falling down lie
along the bottom of the canal, and thus become
the fixed point or lineal anchor on which the owing to the effect of slight variations of tempera- tent of 40 parts in a thousand.

power acts; the action of the engine in dragging the chain over the loose and fixed pulleys being necessarily to drag or propel the boat forward. Every yard of the chain passed over the pulleys

taining eight ounces of water, ninety-nine parts
in the bulb and one part on the tube, which is di-
vided into 100 degs, so that each degree is of the
whole 1-10,100th part, and the pressure of each
30 in. of mercury caused a compression of rather
more than 1 deg. in fresh water, and about of a
degree in sea water. The result varied a little

ture on the bulb. This difference of result, how-
ever, does not affect the principle of the instru-
ment. The compressibility of water is too minute
to be recorded in a simple tube, but it may be re-

corded in two methods; one, with a bulb or bottle

it contains exactily 10 ounces of water.
piston is of such a size that 26 in. would displace
one ounce of water, and is divided into 100 prin-
cipal degrees, which are subdivided, each principle
being 1-1000th part. Of this length a portion of
40 deg. (about 10 in.) has been taken, so that this
instrument can record compression up to the ex-
A spanner

accompanies the instrument, to unscrew or tighten
the packing box when necessary; the other end of
the spanner fits into and turns a tap at one end of
the cylinder, the interior of which is oval, and the

representing a yard of space that the boat has and a tube accurately divided, the tube being tap has a small air channel to allow the escape of

furnished with an index to be pushed along the tube by a cork or elastic piston isolating the water in the vessel, and travelling along the tube towards the bulb during the descent until the isolated water became equally dense with the water surby the expanding water in the bottle, leaving rounding it, and when pushed back in ascending behind the index to mark the degree of compres

air, so that the cylinder may be filled quite full of water. The instrument may then be placed in the accompanying stand, and the cross bar screwed on to the piston, and weights attached to the cross bar showing pressure after deducting the the piston in the packing-box, when the cylinder weight of the two 2 lb weights, together 4 lb., which are required to overcome the friction on is empty. The spring should be relaxed, and the

allowing the escape of the air confined by the cork
index pressed down a little, and afterwards pushed
or elastic piston. The instrument to be fastened up to the piston to prevent the friction of the in-
to a line with the piston downwards, so that the
dex from affecting the experiment. If the two
isolated water, being lighter than surrounding 5 lb. weights, together 10 lb., are used after deduct-
water, should press upwards against the tap rathering the 4 lb. for friction, a pressure weight remains
than towards the piston.
applying the principle has, however, been adopted and the pressure of the 6 lb. upon the piston is
Another method of of 6 lb. The diameter of the piston being ths of an
inch, the area is about Aths part of a square inch,
thus equal to a pressure of 81 lb. per square inch.

on the suggestion of Mr. F. Hoffman, who made

progressed in her course-the fixed point or length of chain lying at the bottom of the canal still remaining the same, what is taken up at the stern being replaced by exactly the same length deposited at the bows. The speed of the vessel is thus exactly equivalent to unless, indeed, there should be any slip of the the speed and size of the driving pulleys, chain in passing over them, and this in prac-sion, a small aperture at the end of the scale tice is easily prevented, and is again exactly measured by the velocity of the chain, unless there should be a slip of the chain along the whole length over the bottom of the canal, and this, of course, is a mere matter of the weight of the chain. In repeated trials which have been made before thousands of spectators (and in more than one of which the writer was on board), in a boat 70 feet long and 7 feet wide, the chain used was only 20 lbs. per yard, or 40 lbs. per yard for the the instrument; namely, to have a tube or cylinder two chains, 22 yards of double chain being always of metal, and in lieu of a scale tube, to use a long at bottom; this gives a weight or resistance of bolt of metal, or, in other words, a long solid 880 lbs. in this case as the fixed point. From the metal piston to enter the cylinder through a data ascertained by Mr. Fairbairn, that in tug. packing box, and to be pressed into the cylinder ging vessels the average pull of a horse was 94 lbs., by the external pressure of the superincumbent the fixed point in these trials would exceed nine water. In descending the piston, when pressed horses' power, and an engine power of nine horses into the cylinder until the density of the isolated could therefore be exerted without the chain slipsea water equalled that of the sea water surroundping over the bottom of the canal. The speed at- ing it would draw along an external scale an index tained ranged from four to six miles per hour, and recording the compression; and on ascending, the nothing more was attempted at that time; the piston, when pushed back by the expansion of the motion was easy and regular, the facility for startisolated water, would leave in its position the ing equal to either screw or paddle, and the power index fixed by a spring acting on a toothed rack of stopping quite peculiar. The moment the enat the side of the scale. In this form the action gine stops she drags at anchor, and the momentum of the instrument appears to be very simple-the is absorbed before the vessel has proceeded onepiston being pressed into the cylinder, or out of it, half of her own length. The weight of chain can according to the relatial density of the water in be doubled or quadrupled without inconvenience, the cylinder and of the water surrounding it; and and the capability of using increased power to any resemble the action of some other hydraulic extent be afforded as required. The weight of presses, although this instrument is worked by chain when increased does not materially increase pressure of the sea, and others by the hydraulic the loss of power, as the power expended in rais-pump. After a correction for the effect of the ing the chains at the stern is neutralised by the friction upon the piston in the packing box, and weight of the falling chain at the bows, the only which is considerable, the instrument appears to loss of power being the friction on the pulleys and record the density or compression of the sea friction rollers as the chains pass from stern to water surrounding it-and consequently the stem of the boat above water, and that must be so pressure to which telegraph lines would be subtrifling as not to merit calculation. The inven- jected at the same depth. tion is not limited in its application to canals, but An experiment of great interest might be made is suited to rivers where occasional shallowness by sending down with this instrument a deep sea may render either paddles or screw useless, or thermometer, and deducting from the total amount where a strong current would prevent any amount of compression, the compression resulting from of power being got except at an enormously in-variation of temperature between the temperature creased and therefore impracticable speed. No additional speed but only an additional power would be required by the chain propeller to stem the strongest current, and however shallow, if the boat will float the propeller will work.

It is almost needless to add that the working of the chain gives rise to none of that commotion in the water that constantly attends the working of both paddles and screw; the chains rise and fall without the least perceptible agitation of the water, and even the ordinary wave from the bow of the boat is cut in pieces by the falling chain and reduced to the merest ripple.

the

of the water and the surface and at extreme
depths, and comparing the balance of compression
with the depth as indicated by careful soundings,
or with some approved instrument, as, for instance,
Massey's sounding instrument. Some further ex-
periments will be required to ascertain the effect
of variation of temperature on the capacity of the
cylinder; and any correction that may be neces-
sary. An endeavour has been made to demonstrate
practically the compression of water by screwing
a small cross-bar into the end of the piston and
attaching weights to it, but as the instrument is

British Association, 1859,

It is to be hoped that after some further experiments to ascertain the effect of variation of temperature upon the capacity of the cylinder, and any correction that may be required, that the instrument will be found practically useful.

ON THE TRUE ACTION OF WHAT ARE

CALLED HEAT-DIFFUSERS.

By ARTHUR A. TAYLOR, of Marscilles. MR. WYE WILLIAMS and others have found that an increased effect was produced by the fuel

burnt in steam boilers when what have been called heat-diffusers were placed in the tubes or flues. The apparatus in question consists generally of matallic bands or ribands twisted into spirals or bent in the direction of their length into zigzag forms, and placed in the tubes or flues, the professed object of this addition being to break up or disturb the current of heated gases passing through the tubes, and to cause every portion of the gases to impinge on the heating surfaces. The cause given for the increased effect produced being, that when a current of heated gases passes through a tube under ordinary circumstances, only the exterior portions of the columns come in contact with the sides of the tube, and that in thus disturbing the current by obstacles to its direct course, a more perfect contact of the gases wit la the surfaces is produced. The question which I wish to raise is, whether this is the true explanation of the effect produced by diffusers, deflecting bridges, &c. I think it can hardly be admitted follows a course parallel with the axis, for those in that each molecule of a gas passing through a tube contact with the sides of the tube will be so impeded by friction as to have a much slower motion current near the banks is less rapid than that in than those in the centre, just as in a river the the middle of the stream; and, that as in the river. tending to bring all portions of the gas in contact so in the tube, a series of eddies will be formeel, with the sides of the tube. This peculiar motio of gases in a tube may very clearly be observed in the smoke issuing from the funnel of

• British Association, 1859,

a

are 75 per cent. less than the usual pumps cmployed for mining purposes. 3. It occupies a very small space. 4. It raises water from any depth with the same facility and economy. 5. It raises with the water, and without the slightest injury to the apparatus, sand, mud, wood, stone, and every object of a smaller diameter than its tube. 6. It is easily removed, and requires no cleaning or attention."

The pump may be seen at Mr. W. P. Warners, Welsh Harp, Edgeware-road (near Cricklewood).

CONCUSSION AND PERCUSSION SHELLS.

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steamer, the smoke retaining the eddying motion which it had in the funnel for some time after leaving it. These considerations led me to consider the mere disturbance of the currents as inadequate to explain the increased evaporation observed, and to attribute it to a very different cause. Gases do not radiate the heat which they contain, so that the only mode in which a gas can communicate its heat to a surface is by contact or connection. This is in the present practice the only mode in which those heating surfaces of a boiler, which are not exposed to the radiation of the fire or flame, can abstract heat from the products of combustion; but if in a flue or tube a solid body be introduced, it will become heated by contact with the gases, and will radiate the heat thus received to the sides of the flue. Now these diffusers, &c., exactly fulfil these conditions, and I, therefore, attribute their effect mainly, if not entirely, to the function which they must fulfil in absorbing heat from the gases by contact, and then radiating this heat to the sides of the tubes or flues, and I think it will be admitted that the amount of heat thus conveyed to the water may be very important, when it is considered that the temperature of the gases in the tubes of a boiler at 5 in. cr 6 in. from the fire-box tube-plates is about 800 deg. Fah., and that these radiators will consequently have a temperature of several hundred degrees above that of the surfaces in contact with the water in the boiler, and that a very active radiation must consequently take place from one to the other. This principle once established. the modes of application in pratice are, of course, endless, and I will only mention that I do not see any advantage in making these radiating surfaces of such a form as to impede the draught, especially in the case of marine boilers, but would rather choose the form which would give the greatest amount of radiating surface, and offered the least impediment to the free passage of the products of combustion through the tubes. Perhaps as effective a form as any for placing in the tubes of boilers would be a simple straight band of metal, or a wider band bent in the direc-which is which.'" tion of its breadth, at an angle of 60°. In the case of marine boilers, they should be made so as to draw out easily, to enable the tubes to be swept.

BASTIER'S PATENT PUMP.

THE following description of an improved chain pump, the invention of M. Bastier, has been sent for publication:

"The chain pump now employed in the Royal Navy has a calibred tube of uniform diameter, and the discs are furnished with leather washers. Its defects are, namely:-1. The resistance caused by the friction of the leather discs against the inner part of the tubes. 2. The rapid decay and alteration of shape of the leather discs, which cannot retain their elasticity. 3. The loss of the water caused by the spaces left empty by the ascending column of water, and consequently loss of motive power, which renders it unfit for mining or other purposes where the water has to be raised from a considerable depth. In T. O. Bastier's new padented pump-elevator the tube is of unequal diameter, that is to say, some parts at a certain distance from each other are of a slightly smaller diameter than the others. This peculiar disposition proves a great improvement. It replaces the piston, and keeps the column of water suspended by causing each disc passing through the smaller tubes to produce sufficient aspiration.' Besides, M. Bastier's discs are furnished with three superposed india-rubber washers of different diameters, which by their permanent elasticity are in continal contact with the inner part of the tubes, and keep them constantly filled. The discs being place about one yard from each other, it has been found practically that the resistance was sufficiently divided to render the action of the indiarubber washers easy and effective."

The following statements are made as to the advantages of the improved pump: "1. It utilises from 90 to 92 per cent. of the motive power. 2. Its price and expense of 'installation'

TO THE EDITORS OF THE "MECHANICS' MAGAZINE." GENTLEMEN,-In page 96 of Captain Jervis's "Engines of War," he states that "Captain Moorsom, R.N. perfected concussion fuzes." Captain Moorsom's sheli was and is a percussion shell. It was I who invented the concussion fuze as far back as 1812. and the select committee of artillery officers at Woolwich were so pleased with its performance that they officially reported that it was 'simple, safe, and efficacious, being well adapted for horizontal fire with high velocities." I gave it the name of concussion fuze to distinguish it from all percussion shells of the spherical form, which latter I considered to be highly dangerous, as has since proved to be on more than one occasion. See former numbers of the MECHANICS' MAGAZINE. I am, Gentlemen, yours obediently, J. NORTON. Rosherville, 24th Oct. Extract from Colonel Beamish's letter to the Editor of the United Service Magazine, August 1859. It is interesting to trace the progress of human invention, to observe the unaided struggles of genius, the frowns of fortune, the rebuffs of ignorant officials; the hope deferred, ' the assumption, presumption, and jealousy of rival aspirants, until the name, and fame, and identity of the original are mystified and overlaid by modern pretenders, and the public are left in the pleasing predicament of not knowing

RULE TO FACILITATE THE USE OF LOGARITHMS FOR NUMBERS LESS THAN UNITY.

TO THE EDITORS OF THE "MECHANICS' MAGAZINE." GENTLEMEN,-Everybody who has worked much with logarithms knows that the raising of powers or extracting of roots of numbers below unity by their aid is attended with some inconvenience.

This arises from the fact that, in order to facilitate the use of the Tables, it is customary not to take the real logarithm of the number, but a certain substituted conventional one. For example, the real logarithm of 0.5 is 0.301030, but as this number is not found in the tables, it is customary to take the log. of 5, and affix to it a minus index, marking it thus: T-698970. This is an anomalous kind of expression, one part being positive and another part negative; and, therefore, it is scarcely to be wondered at that its management should cause trouble.

In multiplication or division by logarithms, the rules usually given, though somewhat confusing, are sufficient; but in involution or evolution with complicated exponents they fail; and it becomes necessary to resort to the true method of working. by finding the real logarithm instead of the substituted tabular one, i.e., taking the tabular logarithm of the reciprocal of the number, with a negative sign.

I venture, however, to propose a rule by which the substituted tabular numbers may be used, however complicated the exponent of the power or root may be:

1. Express the exponent of the power or root in the form of a fraction, whose numerator and denominator are both whole numbers.

2. Having found the substituted logarithm from the tables, and given it a negative characteristic in the usual way, make this characteristic positive, by adding to it the denominator of the above fraction.

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"HOW BIG BEN SHOULD BE SUSPENDED."

TO THE EDITORS OF THE "MECHANICS' MAGAZINE." GENTLEMEN,-Will you oblige me by inserting in the next number of your Magazine a few words in reply to an article in the last number of the Magazine from Mr. Charles W. Lancaster on the subject, "How Big Ben should be Suspended." The method there mentioned by Mr. Lancaster originated from myself nearly two years since, and was at that time communicated to Mr. C. Mears previous to his casting the present Bell. It also appeared in the MECHANICS' MAGAZINE October 7, No. 41, in a letter from Mr. Loseby on Big Ben, and also in the Society of Arts Journal of the same date. I am, Sir, Yours, &c. THOMAS QUARM.

ECONOMY.

THE GREAT EASTERN AND STEAM-SHIP | sult determined after this manner, but that in- | fluence must be ascertained separately, by taking the midship section for the peculiar governing quantity. In this way it is seen that the Great of her form; but at the same time it is seen that Eastern presents no remarkable result arising out the result is so far satisfactory as to permit the other circumstances of her build to have full scope, for a dynamic performance of extraordinary commercial excellence.

TO THE EDITORS OF THE "MECHANICS' MAGAZINE." GENTLEMEN,-Permit me, in addressing to you a few observations on the formula for steam-ship performances, to take the opportunity of adverting first, to an erratum in my last communication, by the omission of part of a sentence, thus rendering it somewhat obscure. I contended therein that in respect to the combination of speed and carry. ing power, "the triumph of the Great Eastern was complete," but the words in italics were omitted. I may add, that her performance was very satisfactory even as to absolute velocity, although it

should be admitted that it never exceeded four

Association.

BENJ. CHEVERTON.

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teen knots; because as your correspondent
"Atlantic" observes, high speed merely was not
the paramount object to be achieved, but eco-
nomic speed, in relation to definite power, and in
relation to such power and burthen; with the
condition, however, that the absolute velocity
should rank with the best steamers of the day.
It was on this point of economic speed, in these
its two relations, that my communication dwelt;
pardon me, therefore, in saying, that your remark
about my forgetting "that a very small (compara-
tive) amount of engine power has been given to
the Great Eastern," does not apply to my obser-
vations, although it certainly is pertinent in re-
spect to absolute speed, and in regard to the
lucubrations of those newspaper reporters to
whom you allude, and who, it is to be regretted, do
not on like occasions hunt in couples, one as the
literary and descriptive, and the other as the
scientific observer, if the union of such talents in
one person is not to be found. It does not apply
in my case, because any variation in the magni-hearted and charitable persons, we take the liberty (being
tude of steam-power embarked in the Great
Eastern ought, if within reasonable limits, to
give nearly the same constants for dynamic per- something more than the relief which, as individuals, we

formances.

Now, is the constant 692, as corrected by yourself, anything extraordinary, seeing that four ships of the Royal Navy exceed it! The formula which gives this constant has for its peculiar governing factor, the midship section of the vessel, and indicates the value of its form. The result, like that of absolute velocity, is satisfactory, and that is all that can be said. But in regard to the third point-the economic speed in relation to power and burthen-the result is successful in the highest degree, and much more I conceive than the constant 292 indicates, although there

is not a vessel in the Royal Navy that approaches
it. The appropriate formula in this respect
giving the above constant is the usual one-
Velocity Displacement
Indicated Horse Power

3

Now, am I mistaken in supposing that this formula, although it may be appropriate for ships of the Royal Navy, does not apply properly to those of the steam mercantile class, and does not do justice to the performance of the Great Eastern in the aspect of commercial excellence, namely, speed in conjunction with great transport capabilities and economic employment of power? It appears to me that this formula does not relate purely to burthen, but mixes up with it the question of section; or rather it infers from the displacement a factitious midship section, instead of the real one, in order that tonnage as well as section should be represented. But surely these two elements should each have its destinctive formula, each excluding the influence of the other, if we would arrive at the merits of a ship in regard to its qualities separately and truly. The square of the cube root of the displacement excludes the influence of the great length in proportion to width for which the Great Eastern is remarkable. It is this, with her great size, and with good lines as a condition, which will give her such pre-eminence in a commercial point of view, and to a degree which no formula within my knowledge sufficiently indicates. Surely what is required is to take the simple displacement as the factor, and not any power thereof. Good lines will no doubt contribute to a good re

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occasion to bring the matter under public notice. If you, Sir, and the public agree with me in thinking such a step desirable, I am sure the authorities will gladly give their consent to the necessary arrange ments; and the friends and admirers of the two Stephensons will not be wanting in their contribu tions. As a justification for putting myself forward in this matter, I beg to add that I was an intimate friend of the late George Stephenson, and that I niso enjoyed the friendship of his son, whom, indeed, a short time before his fatal illness, I had arranged to

May I be permitted to think that the appro-join in a journey through Egypt next month." The following letter on this subject has been re Priate formula for mercantile steam transport is a ceived:-GENTLEMEN,-I quite agree with Sir Joseph subject for the reconsideration of Mr. Atherton Paxton, who has been honoured by Royal distinction and the committee of Section G of the British for minor services, that the nation's gratitude should I am, &c. speak for itself, in the last tribute paid to the honoured memory of both those illustrious benefactors of their country, the Stephensons. Among the earliest and greatest works of the father George Stephenson, was the union of Liverpool with Manchester in less than one hour by railway and locomotive conveyance, thus largely contributing to make Liverpool the greatest port in the world, and Manchester the greatest town in the world for home and foreign cotton manufac tures, besides leading to the formation of all the other railways in this and every other nation. The late Mr. Robert Stephenson stated in his address as President of the Institution of Civil Engineers in 1838 that railway engineers, railway surveyors and railway solicitors, divided between them two millions sterling; and no member of the engineering profession was more extensively and importantly engaged in the execution of these works than the late Robert Stephenson, who with his father, it is said, most deservedly realised nearly half-a-million of money. Among the resuits of the railway and locomotive system Mr Robert Stephenson states in his address that the whole community in the United Kingdom were then saving (1856) in conveyance alone, forty millions sterling annually; and as this saving had been progressing gradually for twenty years previously, the aggregate amount saved may be computed to be at least two hundred millions sterling. The same patriotic and generous spirit which induced Sir Joseph Paxton to suggest a more appropriate resting-place for the remains of George Stephenson, the father, "as the author of the locomotive system," will no doubt induce the wealthy representatives of George and Robert Stephenson to rescue the remains of another illustrious railway and locomotive benefactor from still greater oblivion than Chesterfield, or the monument so generously and nobly intended at Newcastle-upon-Tyne-the only mondment that was erected over the remains of the great man whom I now refer to being the most ordinary tombstone that could be afforded by his widow, scarcely visible and still less legible in the churchyard of Hampstead village-not by removing his dishonoured remains to Westminster Abbey, though very much nearer than Chesterfield, but merely by

AN APPEAL

TO THE SUBSCRIBERS AND READERS OF THE
"MECHANICS' MAGAZINE."
KNOWING that we have the happiness to embrace among
our subscribers and readers a goodly number of large-

fully aware that it is a liberty) of bringing to their notice
a case of peculiar hardship and distress which calls for

have been able to afford it.

Early in 1857, a firm well known to the engineering world prosecuted a clerk of theirs for embezzlement, and got passed upon him a sentence of several years' imprisonment traordinarily heavy in proportion to the offence, on account -a sentence which, as the judge himself said, was made exof the prevalence of such offences just at that time. The wife of this man-a refined and excellent person-was left with no less than seven children to maintain, not one of whom was then contributing towards its own maintenance. Aided by two of her children she has, since her husband's conviction, laboured with the utmost industry, and to the full extent of her ability, to support her family, and has succeeded with the aid of a few friends in doing this until now, despite a long and dangerous illness. Her health is at last, however, sadly broken down, and unless assisted she will even should her life be prolonged.

speedily be no longer able to keep her children about her,

A memorial, praying for a mitigation of the father's punishment, and setting forth in connection with this case other facts to which we need not here refer (which memorial was signed by the present Lord Mayor of London, the Rev. W. Cadman, M.A., of St. George's, Southwark,

Taylor, M.D., W. Cooper, Barrister-at-law, one of the Editors of this Magazine, and others)-was lately presented to the Home Secretary, but for want of the signatures of the prosecutors was of no effect.

Believing that some of our readers might be willing, or even desirous, to contribute towards the relief and aid of this unhappy person and her family, we adopt this method of making the case known to them. Whatever they may be generous enough to send to ourselves (the Editors of the MECHANICS' MAGAZINE, 166 Fleet Street, London), shall be instantly transmitted to the objects of their benevolence, and duly acknowledged in our advertising columns or otherwise. We need hardly say that the smallest gift would help to gladden the mother's heart. We sincerely hope, therefore, we shall not fail to receive many immediate

responses to our appeal.

Our Weekly Gossip.

substituting some humble tablet for the worn-out tomb

stone erected more than 58 years ago, over the grave. The inscription might be :-"This tablet was erected in 1859 by the representatives of the late George and Robert Stephenson, to the memory of Henry Cort, the founder of the British Iron Trade, and Tubal Cain of our country (See Times 29th July, 1859); he departed this life the 23rd May, 1800. Reader, bear in mind this, the humble individual who lies burie 1 here, was robbed of all his property and patent rights by servants of the British Crown in 1788, who were the greatest robbers of the State ever known in English history; yet, without the inventions of this victim to State villany, no railway locomotive, stea n engine, or electric telegraph, for manufacture or conveyance, could have been made available either in the old or new world: nor could the consumers of British iron have saved in the price of wrought iron alone, in the last sixty years, six hundred millions of money." SENEX.

We learn from the Paris correspondent of the Times that Admiral Paris, C.B, of Brest, has been doing good service in connection with the lifeboat George Stephenson should be removed to Westmin- issued from the Paris press, entitled Instructions 827 SIR JOSEPH PAXTON proposes that the remains of system in France. A very useful pamphlet has just ster Abbey. He writes:-" It occurs to me that in la Manoeuvre des Canots. It originally appeared in honouring the son (Robert Stephenson), the father, English as Instructions for the Management of Open who was pre-eminently the author of the locomotive Boats in a Heavy Surt and Broken Water, &e., and system, ought not to be forgotten, but that his re- was published under the auspices of the Royal mains should be removed from the comparative National Lifeboat Institution. The French translation obscurity in which they are now placed to Westinin has been very well done by Admiral Paris, and the ster Abbey, and that a suitable monument should be pamphlet has been extensively circulated on the coasta of France. "I alluded some time since," says the writer erected there in memory of father and son, to whom The just referred to, "to the lamentable want of lifeboats England and the world are so much indebted. removal of the remains of the elder Stephenson was on the French coast, and the offer of the National mentioned to me by some of his old associates not Lifeboat Association to assist the French Governvery long ago, although without any anticipation of ment in this work of humanity. There is not so the sad event which appears to make this a proper | accurate a Wreck Register and Chart kept here as in

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