;

tons, has two engines of 70-horse power each, and employs 22 hands, exclusive of the Captain. Is of opinion, that were the means provided of laying on an extra quantity of steam power, it could be turned to beneficial account in foul weather it is only for want of power that in some circumstances a ship will fall off, when of course you are liable to ship a sea. The vessel might in bad weather be strained by increasing the power, but in smooth water a vessel feels very little the effect of the wheel. Creates very little sea except when in rivers; you then see the water running on the shore, but nothing more. A full vessel always makes more swell than a sharp one; because she passes easier through the water, and makes no ripple: but thinks there is no more swell from a steam-vessel than from a sailing-vessel. There is a ripple proceeds from the paddle-wheel, but it is very little. The Dolphin has a general overhaul at least once every year; sometimes oftener. The wear and tear is greater than in a sailing-vessel; but has gone over three times as much ground as a sailing-vessel would have done in the same time. The wear has been in the engine chiefly; the vessel has suffered very little; her shell has not been at all broken; when last examined she was stripped to see whether the beams parallel with the boilers had suffered, but was found there, and every where else, perfectly sound. The boilers had been worked two years and a half before it was found necessary to take them out to have a thorough repair. The greatest speed witness has ever gone was 11 knots-not quite, but very near. Thinks his packet is capable of carrying 500 passengers, which is not quite 2 to a ton. A vessel may carry, without being overloaded, 2 to a ton (builder's measurement), but not

more.

Would reckon a horse, or any horned animal, as equal to 5 men, supposing the horse to occupy the same space as on board transports, namely, 20 inches. Believes that the steam-boats between England and Ireland frequently exceed these rates; has seen a 300-ton boat carrying 700 passengers, besides a cargo of goods in the hold. Does not think it would be possible to make any regulation as to a vessel being brought down to a certain depth.

191

To Mr. Hunter, for the best Essay on Political Economy, £6.

To Mr. Price, mathematical--instrument maker, for the second best on the same subject, £4.

Both prizes the gift of T. H. Holdsworth, Esq.

To Mr. Francis Clifton, for the best Essay on Emigration, £10. The gift of Bingham Baring, Esq., M. P.

To Mr. Ward, engineer, for the best Essay on the Effects of the Distribution of the Revenue on the Condition of the Working Classes, 10. Donor anony

mous.

To Mr. Colliver, a smith, a prize for Architectural Drawing.

To Mr. Curtis, an operative, a prize for a Drawing of a Steam-Engine.

A Resolution was proposed by Mr. Josiah Conder, and unanimously agreed to, declaring the objects of the Institution to be, "the extension of civilization, and the increase of human happiness, by unfolding and enforcing the great truths of social and physical science; excluding only those topics which by their local, temporary, or personal influence, are calculated to interrupt the harmony and well-being of society."

THE BRITISH ALMANAC.

Dear Sir Perceiving that you have made a mis-statement at p. 159, relative to the British Almanac, I consider it due to you and the public to let it be corrected. By some inadvertence, you have given me credit for being "one of the Committee of the Society under whose superintendence this almanac is published;" but al though I consider it at all times a great pleasure to encourage and promote scientific and useful knowledge in every direction, I have not the honour of being one of the said Committee; and from the high opinion I entertain of many whose names are on that list, I feel satisfied that the omission I have called to their notice will be readily supplied in the next almanac. I should hope, also, that they will find a small corner for the declination and right ascension of the planets about five or six times in the month. This trifling addition would enable young ladies and others to solve many useful problems upon the globes, which they cannot do at present without

[We have reason to believe, that we do not stand alone in the mistake here pointed out. We were led into it, as others have doubtless been, from observing in the list of the Committee of the Useful Knowledge Society under the head of "Bury St. Edmund's," the name of "B. Bevall, Esq." The similarity between that and the designation of our esteemed correspondent-nay, the perfect identity of the names, and the abbreviated mode of subscribing them-caused us to overlook the difference (which is, besides, not great) between the locality of Bury St. Edmund's and Leighton.-ED. M. M.]

Maelzel's Metronome-Sir, Your interesting Journal is so ready a medium of intercourse on all matters relating to science, that I trust you will allow me to avail myself of the Mechanics' Magazine to suggest to some one of your ingenious readers, the great want that exists of some instrument which should answer the purpose of Maelzel's Metronome, but be purchaseable at a much cheaper price. Your readers are doubtless aware, that the instrument to which I refer, acts much upon the principle (I believe) of a clock, and by means of a spring and pendulum, marks the various divisions of time in music, adapted to the several movements, from the lento to the quickest measure. These instruments cost the enormous price of ten guineas; and thus are received into very limited use, the parents of children, and even amateurs themselves, being little inclined to be at so great an expence for so secondary an instrument. I trust, therefore, that the ingenuity of some one of your mechanical readers may be excited by this hint; for if an instrument, equally effective, could be procured for a guinea, I feel convinced a handsome fortune might be made by the invention.-Yours, &c., PHILOMUSICUS.

Maps of Cities.-Sir, I must say I was rather astonished at the virulent attack upon my invention by F. H., especially as he himself comes to the very same plan in the end. He says, maps with large squares marked with letters are common. True, I have seen them, but they are insufficient; only making, as it were, a smaller map of each square. He then advises that the squares should be made smaller, which is exactly the same; or, if any thing, a more troublesome mode than mine. Then as to the awkward large rule, it may be half an ounce weight, made of pasteboard with a leather joint in the middle of each limb-or even of ivory, which might be made very small and neat, But I only hinted at the use of a rule, for a book or any other rectangular body would do equally well. As to F. H.'s mentioning the use of them in France, he describes a map like the common ones here, and equally inferior to mine. Having, I hope, proved that my maiden invention is neither so old, ner so awkward a contrivance as F, H, thinks it, I lay down

my defensive weapons, and remain, Sir, Yours, &c., LECTOR.

Influence of the Moon.-Sir, I shall be obliged to any of your correspondents, who will have the goodness to inform me whether the observation of the extraordinary influence of the moon on fresh killed animals, fruits, trees, &c., that appeared in your 4th vol., No. 108, page 381, September 17th, 1825, has ever been accounted for, or any further explanation attempted. I shall likewise feel particularly indebted to any one who will transmit any information on the subject, prior to my furnishing you with some remarks, which I have collected, and made on the influence of the Moon.-Yours, &c., L. C.

Note Explanatory.-Sir, I take Iver Maciver's observations in very good part, because 1 am persuaded they are well meant; and, therefore, shall not quarrel with their style. My answer to Iver must unavoidably be short; but I trust he will not on that account think it uncourteous. I am aware that in your pages I stand almost, perhaps quite alone in some of my observations on locomotive-machines. I must leave Iver to form his own opinion of my natural talents, and acquired knowledge, and in the undisturbed possession of that opinion when it is formed. Any one is welcome to acknowledge or deny the truth of my statements according to his judgment; but I cannot undertake to satisfy every one of the propriety of the manner in which those statements are made. I deem it unnecessary to re examine or re-consider my observations in No. 430, but if Iver, or any one else, will make manifest any error I may have committed, I shall at once acknowledge it, and feel myself obliged to him for correcting.-Yours, &c.. S. Y. an Engineer, Dec. 3, 1831.

The Cholera.-Sir, It is a remarkable fact, that when St. Petersburg was visited with cholera, not one of a certain regiment of soldiers (whose name I forget) suffered from its effects; a circumstance which was thus accounted for :-Part of the accoutrement of a private consisted of a wide belt round the waist, which belt was made of a coarse substance not unlike to a strip of blanket, only polished and decorated on the exterior. And this, it was supposed, was such a comfort to the bowels, and such a protection to those parts which are most liable to the first attacks, that the whole regiment, to a man, was saved; and although a few were attacked, yet the disease was not so malignant in those few cases as in the generality of them,-Yours, &c., CHARLES JOHN M'KENZIE, Vittoria Cottage, Nov. 29, 1831.

WITTY'S IMPROVED AIR-PUMP AND ELAS

TIC FLUID CONDENSING APPARATUS.

Sir,-The complexity of the valves in what are considered the best air-pumps, and their many defects when it is required to obtain a perfect vacuum; and the difficulty of carrying the compression of elastic fluids to a great extent of pressure, except by the hydro-pneumatic pump, invented, I believe, by Mr. David Gordon (see note at the conclusion); have led me to reflect on the subject; and I beg leave to offer the following arrangement, which I shall be happy to see inserted in your valuable Magazine.

R is a receiver; P, a tube with two branches, communicating with the receiver and the two cylinders, A and B. KK, two piston-rods, working through stuffing-boxes ii; rv, two pistons, which are solid, and tightly packed; the bottom parts of each of these pistons are accurately turned of a conical form, with a stud in the centre projecting downwards about half an inch. oo, are two valves, also conical, which perfectly close the bottoms of the cylinders; these valves have hollow shanks with spiral springs in them, and slide in two little cylinders, which serve as guides DD, two short cylinders, into which the cylinders A and B are fixed by flanges, and the ends of which descend about three inches into these short cylinders, which are filled with quicksilver to within an inch of the top, marked black in the drawing. T, a tube with two branches, which are firmly screwed through the lower flanges of the cylinders A and B, and communicate with the air above the quicksilver. U, an union-joint; C, a cock; ff, two friction-rollers; e, a screw to re-admit air into the receiver B. The handle and cog-wheel which give motion to the pistons are omitted in the above drawing, to render the references more clear.

Such being the construction, the exhaustion takes place in the following manner :-When the handle is turned so as to bring the piston r to the bottom of the cylinder, then the piston v will be carried just above the orifice of the tube P, as represented in the drawing; and when the handle is turned the contrary way, v will be depressed, and a will be raised above the orifice of the tube P in the cylinder A. Now, upon the descent of, it must manifestly force all the air in the cylinder B before it, the sides be

ing air-tight; the air, therefore, will be forced through the valve o, and rise in bubbles to the surface of the quicksilver; when the piston arrives at the bottom of the cylinder, the stud in the centre of it will depress the valve about half an inch, and every particle of the air will rise to the surface of the quicksilver; it will then be in the position of the piston æ in the drawing, all the air expelled, and surrounded with quicksilver. Then elevate v, and depress x, which, in like manner, will force out all the air before it. Now, as v ascends, the valve o, by means of its spring, will follow till it touches the conical edge of the cylinder B, and include a small portion of quicksilver, when the bottom of the cylinder will be perfectly closed; but should this valve leak a little, nothing but quicksilver can get through, which would not be at all injurious; the piston v still rising, a perfect vacuum will be formed between the valve o and the piston v, but when has passed the orifice of the tube P, the air will rush from the receiver R into this vacuum, the consequence of which is, that the air in the receiver becomes rarified by being expanded into a greater space, and as this must take place every time each piston descends, or at each turn of the handle, there must be a continued exhaustion, and consequently a continued rarifaction of the air in the receiver, because every particle of the air below the piston is expelled at each stroke; when the vacuum is complete, the cock C is to be turned.

บ

I have read a description of Cuthbertson's air-pump, which is a most ingenious machine, but the complexity of its parts, liability to be out of order, and expense, are great objections against it. The air-pump of Mendelssohn, though complex and expensive, is more simple; but as it does not expel all the air between the piston and cylinder top, it cannot be considered a perfect machine, for the small portion of compressed air may be sufficient to fill the cylinder with air of as great or greater elasticity than the air in the receiver, when further exhaustion is at an end. Now, this is the great defect of all air-pumps I am acquainted with, and all pumps for the compression of elastic fluids excepting the hydropneumatic pump, which I have mentioned.

The apparatus I have devised will, it

is presumed, completely effect the desirable object of continued exhaustion, that is, as far as the air has sufficient elasticity to expand into the cylinder. It is evident, that this air-pump may be immediately converted to the purpose of condensing air or any other gases, either by unscrewing the joint U, and uniting it to the tube T, which may be made to fit, or by having a separate pump-plate, when the operation of condensation and exhaustion might go on at the same time: but this I should not recommend, as the too great compression of air below the pistou might force a small portion through the packing, which would prevent a good vaccuum being formed. When it is required to compress gases, the tube P should be connected with another tube coming from A, gas-holder or pneumatic trough, and as every particle of air or gas is expelled the cylinder at each stroke, and under whatever pressure, compression may be carried to an unli mited extent.

195

part, c, is filled with water; the darker part, dd, with quicksilver. When the plunger is drawn up, the water spreads into the space which the plunger occupied; aud the inferior column of quicksilver being thus relieved from the pressure of the water, rises in the long arm of the syphon, and sinks in the short arm, till it attains the same level in both. In consequence of this depression of the mercury in the lower arm, the valve e opens and lets in a volunre of gas of ordinary density, which flows from a gasholder through the pipe f. On the down-stroke of the plunger the gas is compressed by the consequent rise of the quicksilver in the short arm of the syphon, and forced through the discharge-valve g, which opens into the pipe, which conveys it away to a suitable recipient. The quicksilver and water are poured in by means of the funnel at, the aperture at k being opened at the time to allow of the escape of the air. When the pump appears quite filled, the aperture k is made air-tight by a screw-plug. Another plug is then screwed into the orifice water above it.

with

THE COMPANION TO THE ALMANACK, OR YEAR-BOOK OF GENERAL INFORMATION FOE 1832.*

PART 1. comprehends, " Information connected with the Calendar and the Natural Phenomena of the Year; and with Natural History and Public Health."

The most important article under this head, "On Eclipses," contains a list of all the eclipses of the sun and moon which will take place before the end of the present century. It seems founded on one which appeared in the "Imperial Almanac" for 1826-an almanac commenced by the Stationers' Company on a plan of utility exclusively, but which was dropped after a few years trial for want of adequate encouragement. [Perhaps it was in advance of the spirit of the age; perhaps not; a little more fuss about it may have been all that was wanted; John Bull is a strange animal, and even when best disposed, is apt to think it infra dig. to move a foot unless at the solicitation of a "world in arms," or out of respect to some approaching whirlwind or comet.] The article is on the whole, however, more complete than that of which it is an imitation. Of its correctness we do not feel so well assured. We have not time to verify a whole century of calculations, but we have examined the first eight, and find two of them quite erroneous. 1832

Jan. 6," should be, "1833 (Jan. 6." The eclipse is made to occur a year too soon. So again, " 1833 June 7," should be, 1834 June 7," the eclipse being again announced to appear a year before its time.

PART II. Consists of "Information on

* Published by Charles Knight, under the superintendence of the Society for the Diffusion of Useful Knowledge.