types, after they have been formed by the usual process. The general outline of the process, of which no details have yet been published, consists in covering each portion of the plate with a coat of transparent colour, of the required local tint, in water-colours, and washing off the excess of non-adherent colour almost instantly in warm water; enough adheres -it appears, in fact, to sink into the plate to give all the effect, it is said, of a very finely finished, but peculiar looking water-colour drawing. The applications to forgery, it may be added, which Möser's discovery will soon afford, will, before very long, render new and difficult means requisite to prevent it in the preparation of bank notes, bills, &c. I think a very small share of common sense, rightly applied, will enable every impartial reader to perceive that this would not only be an expensive, but really a needless remedy. Either the objectionable deposits in the water pipes are capable of being acted upon and removed by the water, or they are not. If they are capable of being carried off by the current, it is only necessary to get that useful functionary "the turncock" to open a plug or two on the lower levels of the district, to get rid of the offending matters at once. But, if there be any deposits that are of such a ponderable character as not to be moved by the rush of water towards these large orifices on a low level, we may depend upon it, they will never annoy us by ascending through the instrumentality of a more moderate stream into our elevated cisterns. The remedy referred to above, is the one that is almost daily employed in various parts of the metropolis, and is so efficient for the purpose, that there is really no necessity for taking up, either Sir,-Having recently visited a neighbourhood where a canal, depending upon casual supplies, is often, if not always so low towards the end of summer as to allow of no more than half cargoes being brought up, and that, often, at the expense of six or eight horses to drag the barges by sheer force over the bottom, it was suggested to me by a gentleman, that rollers might be advantageously applied, and upon consideration, I beg to submit, through the medium of your valuable Magazine, the following plans for the comments of those practically acquainted with the subject of canal navigation, of which I freely confess my own ignorance. My object would not be materially to increase the cargo at such times, but merely to render a much smaller amount of power necessary to drag the barges over the flats. I propose to furnish each flat-bottomed barge with three or four, or any other number of castiron rollers, say, 6 or 12 inches diameter, running on pivots, 6 or 12 inches long, at certain distances along her bottom, on each side about half way between the keelson and the extremity of her bottom, such rollers to project only such a distance as may be deemed or found most advantageous, and to run in recesses constructed in the bottom for the purpose, which could be easily contrived. It may be objected, that the rollers would be useless in muddy bottoms, but I would submit, that as mud accumulates generally in the holes, or deeper parts of water, leaving the shallower parts free from it, the cbjection, taken generally, does not militate against my plan. It is not improbable that some such may already be in existence, of which myself and neighbours would feel obliged for an account. I remain, Sir, yours, respectfully, Oakham, November 19, 1842. FOUR-WHEEL LOCOMOTIVE ENGINES, and the EFFECT OF INSIDE AND Sir,-Being constant readers of your We take leave to advert here briefly to your article in the October Number, headed "Progress of Foreign Science,' on the subject of the Versailles railway accident, of the 8th of May last, in which you gave a garbled extract of M. Se- BURY, CURTIS, & KENNEDY. P.S. We enclose a lithographed sketch of the effects of inside and outside framing, with the broken axle, which illus trates what you are pleased to call "the singularly ill contrived and inconclusive experiment on the London and Birmingham Railway," and which we think will convey some instruction of an useful and interesting nature to your readers. [We give on the opposite page the engravings referred to by Messrs. Bury, Curtis, and Kennedy, and subjoin their explanation of the figures.] The effect of inside and outside bearings practically explained. Figs. 1 and 2. Locomotive engine with inside framing. Figs. 3 and 4. Locomotive engine with outside framing. Figs. 1 and 3. Show the position of the wheels with the axle broken. Figs. 2 and 4. Show the position of the wheels in both engines when running on the railway. Explanation of Figs. 1 and 2.-In this engine the bearings are inside the wheels, and the weight of the engine and boiler is carried at A A. The tendency of the axle, therefore, is to bend downwards in the centre, whilst the pressure of the flange against the rails in How "garbled!" Imperfect it may possibly be; but garbling implies intentional misrepre sentation, and every thing of the sort we most distinctly disclaim.-ED. M. M. going round curves, has a contrary tendency. Thus one strain counteracts the Fig. 1. effect of the other, and if the axle breaks, the wheels can spread out no farther Fig. 3. pressing against the inside of the rails, may proceed with safety to the next station.* Explanation of Figs. 3 and 4.-The gravity or insistent weight of this engine with outside frame is carried at B B, outside the wheels. The gravity of the engine and boiler in this case tends to bend the axle upwards in the middle, and the pressure of the flange of the wheels against the rails in going round curves, acts in the same direction, and in addition to it. This continued bending of the axle destroys the fibre of the iron, and ultimately it breaks; and when it is broken, the tendency of the axle upwards, as before shown, forces the wheels between the rails, there being no flange outside the wheels to prevent it, as is shown in fig. 3. Sir,-The following experiments illustrating certain effects produced by the explosion of gunpowder, may be interesting to some of your readers. Being exceedingly fond of rifle-shooting, it so happened during a morning's practice, that the ball became so fixed in the barrel at a short distance above the charge of powder, that I could not, with the implements then present, force it "home.' I had often heard of guns bursting from similar incidents, but having duly surveyed the substance of the metal around the bore of the barrel, I thought-well, this cannot burst. 1st average, powder and ball alone The rifle was very small, having two grooves in the barrel, and carrying a ball weighing the th of a lb. avoirdupois. The charge of powder was 20 grs. of the best quality (" extra canister"); the target was a wrought-iron plate inch thick; the distance was 100 yards, and the usual effect upon the target was the slightest possible indentation of the surface upon which the ball impinged, (the ball being smashed to atoms). On this occasion, however, the ball all but perforated the entire substance of the plate. The indentation was deep and conical, bursting open the opposite sur face of the plate. It immediately occurred to me that this unexpected result might be turned to advantage, by making barrels so strong that, instead of the thus increased force of an ordinary charge of powder being spent in bursting the tube in which it might happen to be exploded, it might be expended in propelling its ball. I therefore had a small cannon manufactured of twisted wrought-iron, and bored from the solid mass, leaving the substance of iron around the bore so thick that it could not be injured by any method of exploding gunpowder within it. Its bore was 11 inches long, and its calibre suited a ball weighing rd of a lb. avoirdupois. It was charged with 56 grs. of Curtis and Harvey's "canister powder," and it was fired at a target composed of 8 planks of half-inch elm board, under the following circumstances, each experiment being repeated three times. The distance was 10 yards. 5 do.. 6 do, and 2nd do. with air equal half bulk of the powder It may be asked how I ascertained that the bulks of air included above the powder were precisely such as I have reported them to have been? In the first place, I prepared some cylinders of cartridge paper which exactly fitted the bore of the cannon, and having ascertained the requisite length of one of these cylinders to contain just 56 For some remarks on this point, see page 572 of our present Number.-ED. M. M. 5 do. (barely). and into 6th 6th 7th grs. weight of powder, I divided each cylinder as it revolved in a lathe upon a wooden mandril into lengths proportioned to the volumes of air they were intended to contain. Over one extremity of each cylinder thus cut and regulated, I pasted a slip of very thin muslin. In loading, the powder was inserted through a brass tube, the gun being held perpendicularly. The paper cylinder was then slid down upon the powder with the closed end downwards. Above the paper cylinder a piece of mill-board, cut with a gunpunch of the precise diameter of the bore, was inserted, and above this the ball was placed, and retained in its situation by means of a circular piece of thick card. Previous to each discharge, the gun-carriage was fixed firmly to the ground by an iron rod, that any errors from the recoil of the gun might be obviated. Although these experiments are of too rough a nature to give the exact effect of each discharge, they still afford an ample illustration of the limits within which air can be advantageously combined with gunpowder for practical purposes. It appears that about equal bulks of air and of powder produce the best results; and this relative proportion of air seems to increase the explosive force of gunpowder by about the one-fifth of that which would have been obtained had the air been altogether excluded. Hence 20 per cent. of gunpowder may be saved, the effects remaining constant; or the usual charges of powder being retained, their effects may be increased nearly in the ratio mentioned above. This principle may be economically adopted either for propelling balls or for blasting rocks. Yours very faithfully, CHAS. THORNTON COATHUpe. Wraxall, near Bristol, December 8, 1842. P.S. I have other experiments connected with this subject in contemplation, the results of which you shall have in due time, if they should appear worthy to be recorded. C. T. C. [We need hardly say that we shall be very happy to receive an account of the further experiments mentioned by Mr. Coathupe.-ED. M. M.] THE WATER QUESTION-FILTRATION v. MONOPOLY. Sir, I promised some time ago to reply to the "last words" of my veteran opponent Mr. Baddeley, but being suddenly summoned to France, I found no opportunity of doing so, and now, on reviewing the former correspondence, I find that nearly every point of importance has been conceded, and that nothing remains for me to do but merely to acknowledge that the frequent cleansing of cisterns is doubtless a very good thing, though the discovery may not be quite so profound as to entitle the discoverer to claim the laurels of a Newton or an Arkwright; but be that as it may, even such as it is, it is no discovery of Mr. Baddeley's, as evidence is already before Parliament of a similar recommendation having been given by the West Middlesex Water Company, as a ruse to induce its customers to lay the blame of the dirt and filth they find in their water on their maid servants instead of on the "monopolists." If your readers or Mr. Baddeley's partizans require proof of this, they may turn to the "Report of the Select Committee of the House of Lords appointed to Enquire into the Supply of Water to the Metropolis," and they will find in the evidence of Mr. W. Clapp, surgeon and vestryman of Marylebone, the following answer : 66 The West Middlesex Company have attached a notice to their receipts, stating that if persons who use their water will keep their cisterns clean, they will find a very great improvement. Now I am perfectly willing to acknowledge that the water is much clearer to the eye than it used to be; there are not so many visible insects, not so many shrimps swimming about it, nor so much mud mixed up with it, but the water is equally impure." So much for the originality of Mr. Baddeley's improvement, about which he chuckles with so much complacency, and to which he attributes such magical influence in causing a ten times greater number of cisterns to be cleansed now than was formerly the case, a circumstance (if true) which proves the great influence of the Mechanics' Magazine rather more than the science or skill of its particular correspondent. Mr. Baddeley must put the laurels he has been displaying somewhat too ostentatiously into his pocket, the West Middlesex Company having a prior right to them. But now comes another champion of the monopolists, with the initials S. R. B., a great epithet-monger, or, as Mrs. Malaprop would call him, "a nice deranger of epitaphs," and he, forsooth, must hurl his ponderous wit against all who will rather prefer not to drink water charged with the filth of a hundred thousand temples of Cloacina, besides divers masses of decomposed vegetable and animal matter, if they could get it in a purer state. Alas for the champions of the monopolists! One and all discover the cloven foot almost immediately on their entering the lists. This worthy gentleman, who really thinks, after all, that water may perhaps |