EFFECTS OF THE LATE FROST-WATER SUPPLY, &C. Sir,--The winter season may not inaptly be termed the plumbers' harvest, and that of the present year has been a most abundant one; I should think the bursting of pipes, &c. has hardly ever been exceeded. Some persons have been so fortunate as to escape the inconvenience attending these accidents, while others have been deluged by two or three leaks in different parts of the house at the same time. The mischief in the streets has been very great. In passing down Cheapside the other day, I observed seven different places in the paving, through which the water was bubbling up: bringing up with it, continually, portions of the cement, and also the finer particles of the gravel, which forms the bed of the road-way.* The traffic passing over these places while they were thus subjected to the action of the water, soon caused a visible sinking of the pavement. The same remark will apply equally well to most of the other public thoroughfares of the metropolis, and a method of preventing similar effects in future is, on many accounts, a great desideratum. In the majority of these cases, the leaden supply-pipe has not burst, but has been driven out from its insertion in the iron-service main. Cannot some better mode of connexion be adopted? I have oftentimes remarked that the connexion at present employed, a common spigot and faucet joint, is not adequate to the increased pressure which the iron mains, now, in many cases advantageously used, admit of. The New River Company's daily supply of water to the metropolis, is estimated at 13,000,000 gallons; but if the usual consumption is reduced two-thirds by the pipes being frozen, and therefore completely closed, and the company continue to endeavour to force the usual quantity of water into their mains, it is evident that a greatly increased pressure will be thrown upon those pipes that do remain open; and if this pressure be continued, some For a description of the mode of paving there employed, see note at page 37. 459 thing or other must give way. I well know that the pressure upon the mains, from this or some other cause, has been unusually great during the past month, and the consequent mischievous effects are plainly visible, both within doors and without. The supply of water should be moderated, and the pressure diminished during the prevalence of severe frosts; because, even were all the pipes to continue open, the consumption of water is always considerably diminished at such periods. The introduction of iron in lieu of wooden mains effected a complete revolution in the water supply; but, notwithstanding this great improve ment, there still remains plenty of room for more; and if one season of the year shows the truth of this assertion more forcibly than another, it is that which we have lately encountered. I am, Sir, Yours respectfully, February 10, 1830. MR. GRAY AND THE RAILWAY SYSTEM. Sir,-In your comments on my railway-system, you greatly err in representing it to be my opinion at p. 333, Mag. 334, "that cog-rails are preferable to plain-rails." No part of my work or of my circular can bear such an interpretation. You seem to think, also, that the recent experiments on the Liverpool and Manchester Railway will satisfy Mr. Gray that on the first point he is much in error, (see p. 333, Mag. 334.) On the contrary, the experiment convinces me more and more of the superiority of the cog-rail-as the same vehicle, by the additional aid of the cog-rail, would have impelled 120 tons instead of 35. By case-hardening the surface of rails and the rim of all carriage be most materially diminished; wheels, the friction upon railways may and then by concentrating the power of the locomotive steam-engine to one specific point, by the introduction of one single line of cog-rail in the centre of the two plain rails, the simplicity of Yours respectfully, Nottingham, Sir, In the conclusion of your reimarks on Mr. Gray's railway-system, p. 334, you evidently do Mr. Gray great injustice, as his work is founded on the practical results of Blenkinsop's patent steam-carriage railway, established at Leeds, as far back as 1811. Mr. Gray's petitions to government in 1820, 1821, and 1822, (see his 5th edition now before me,) most clearly establish, that years before The Scotsman wrote, Mr. Gray was actively engaged in disseminating the important principles of his railway-system. I am much pleased that you enter with so much spirit into the railway-scheme, as I firmly believe that nothing can contribute more to our internal wealth and prosperity. By the insertion of these few lines in your valuable Magazine, you will greatly oblige, Your constant reader, Market-street, Manchester, [We have not disputed the priority of Mr. Gray's efforts, nor withheld from him the praise which is justly due to him on that account. All that we said was, that they had "not the good fortune" to produce so great an impression on the public mind" as the papers subsequently published in The Scotsman, and this Mr. Gray himself does not deny.-ED. M. M.] THE ELECTROPHORUS. Sir,-Several of your correspondents have sent you descriptions of small electrical apparatus, but no one has ever mentioned the electrophorus; at which I am rather surprised, as it is much better than either the tube or the riband plan in your Magazine. B The handle A is either of glass, or of wood with a glass nut at the bottom (made black in the diagram), and is fixed to the circular plate B, made of block-tin, wired at the edge, or, if elegance is required, of polished and lackered sheet-brass. The lower plate C may be made of a variety of substances; but I give the neatest and best. Get a circular board turned of any hard wood that will not warp, about half an inch thick: then melt in a ladle several ounces of common sealing-wax, and pour it, in a liquid state, over one side of the wood, so as to cover it completely. Make the surface level by heat; a hot smoothing-iron, or a kitchen "salamander," held at a little distance over it, answers admirably. Coat the opposite side of the wood with tinfoil, and the work is complete. To put it in action, take a piece of warm flannel, and rub con spirito, the sealing-wax: then place upon it the tin-plate, holding it by the handle. Touch the plate with the finger (it will not do without) as represented in the sketch; take the finger off, and then raise the plate by the glass handle, and it will give out a strong spark, which may be communicated to a Leyden jar. Many pretty experiments may be done with this little apparatus besides stunning a man's arms up to the shoulders. Being once well rubbed, it will continue in full action several hours, without being rubbed again: this is one of the most curious circumstances attending it. The description of all its powers fills upwards of four quarto columns in the "Encyclopedia Britannica." Of course, the larger the two plates are made, the greater will be the power; 9 or 10 inches in diameter is a very good size, and it is recommended that the lower plate be about one inch more in circumference than the upper. With one of these dimensions, an active operator may VELOCITY ON RAILWAYS. 461 VELOCITY ON RAILWAYS. Sir,-If R. C. Jun. will take the trouble to read attentively the papers in your Magazine on the railwayquestion, he will find that his observations in No. 339, have no more to do with the subject in dispute than with the dome of St. Paul's. When a carriage is to be moved, there are three resistances to overcome: 1. that arising from the inertia of the carriage; 2. that arising from the resistance of the air; and, 3. that caused by the friction of the moving parts. Now, the observations and calculations of Dr. Wood, as quoted by R. C., were intended to explain and measure the effects produced by the inertia of the body, considered abstractedly. The subject in dispute was the quantity of mechanic power equal to the resistance caused by friction only; to measure which, Dr. Wood's calculations were never intended, and are completely inapplicable. R. C. will also find, I think, that his ideas were a little confused when he wrote his letter. In the beginning he seems to understand the question to be the effects of friction. He then "imagines" the question to be what it manifestly is not-enters into calculations which apply only to the effects of inertia—and ends by observing, "if the effects of friction be traced," &c. &c. If the effects! Why, good Mr. R. C. Jun., they were the only effects which The Scotsman, or his opponents, were at all concerned about. As R. C. has so completely misunderstood what it was which your correspondents attempted to establish, his observations on the methods they pursued of course pass for nothing. I am, Sir, Respectfully yours, Feb. 6, 1830. S. Y. (An Engineer.) STATEMENT OF EXPERIMENTS MADE WITH WINANS' RAILWAY-WAGGONS. We have been favoured with the following abstract of another important set of experiments, made in the latter end of January, by Mr. Vignoles, engineer, to ascertain the exact amount of friction of railway-waggons, made on the plan of Mr. Winans', as described in our 328th and 333rd numbers. We are informed that Winans' small waggons were those used by Mr. Vignoles when he made his experiments on the power of "The Novelty," as stated in Number 339; and that Mr. Vignoles assumed from the state of the rails on that occasion, that the rolling and axle-friction was about six pounds to the ton. But in this estimate he did not include the lateral friction, and made no allowance for the retardation arising from so long a train of waggons not connected together (as we understand they will be in practice) by bent springs to prevent shocks, &c. The comparison of these two sets of experiments we consider highly interesting, and eminently deserving the attention of scientific men. From a rough calculation of our own, we are inclined to think that the total expense of fuel, wear and tear of locomotive engines and waggons, will not exceed 1-3rd of a penny per ton nett per mile.-ED. M. M. Abstract of Experiments. The mean of a series of experiments made with one of Winans 20-inch wheel waggons, without springs, weighing about 12 or 13 cwt., and loaded with 2 tons, shows that the waggon, after being only just put into motion on the foot of the inclined plane at Whiston, ran over 932-59 feet in 232 seconds, the perpendicular fall in which length was 243 inches. Several of the individual experiments agreed within a fraction of the above mean. 931-59-452 2.06 Now. 462 EXPERIMENTS WITH WINANS' RAILWAY-WAGGONS. friction in a ton, or a force of 5 lbs. would move a ton. The above inclined plane fell 18 inches in the first 200 feet; 6 inches in the next 500 feet, and of an inch the succeeding 200 feet; the remainder of the distance being quite level. The initial velocity was 2 feet per second, the maximum acquired velocity 7 feet, and the terminal velocity 1 foot per second. The rails in these experiments were free from absolute dirt, though not perfectly clean; they were somewhat oxidized, and on the whole, may be considered as having been in the state they will be practically found in when the road is travelled over by trains of waggons drawn or propelled by locomotive steam-engines-no horses working on the railway. On a succeeding day the same waggons, similarly loaded, were tried on the two-mile level at Rainhill. Upon this occasion, the rails were in far superior order, and may be said to have been perfectly clean, and free from every particle of dirt or impurity, A weight of 10lbs. freely suspended over a 2-inch pulley, kept up the momentum of the waggon (when once put in motion) at the rate of about 2 miles per hour. The exact weight of the waggon and load was 624 cwt. or 7000 lbs.; therefore as 7000:2240:: 10.75:3-44lbs. friction in a ton, under the most favourable circumstances for small wheels: but as in the practical use of such wheels they will always be to some extent retarded by minute impediments which will not affect large wheels, it will be more proper to state the total rolling and axlefriction of Winans' 20-inch wheel waggons at these velocities as not exceeding 5 lbs. in the ton. It is clear, from the experiments of Coulomb and others, that the friction is not increased by an increase of velocity; but it is probable that at high speed, and with a long train of waggons, especially if they are without springs, oscillation will take place to a great extent, and cause a rubbing, or lateral friction, of several lbs. in the ton. This lateral friction is also increased by too much conicality upon the rim of the wheel, and is applicable to all descriptions of railway-waggons, though in what proportion as regards the diameter of wheels and axles, flat or conical rims, common fixed axles, and those on Winans' principle, remains to be deter mined by future experiments. On the same day, with the small wheels, other experiments were made with Winans' 3-feet wheel-waggons fitted up in the best manner, but without springs under the body of the waggon. The results on the inclined plane showed that the waggon being only just put into motion, passed over a space of 824-67 feet in 275 seconds, the perpendicular fall in which length was only 11 inches, or 0.92 feet: of this fall, 7 inches occurred in the first 200 feet-3 inches in the next 550 feet and only half an inch in the last 75 feet. The initial velocity was 2 feet per second; the maximum acquired velocity 4 feet per second; and the terminal velocity 8 inches per second. The same waggon on the perfectly clean and level railway, and weighing with its load 804 cwt., required only 93 lbs. to keep up the momentum (when put in motion) at the rate of 2 miles per hour. The result, therefore, by the inclined plane experiments, or 824.67 0.92 896, shows that the 3-feet wheel-waggons will roll self-acting 2240 lbs. in a ton, in a ton. 25 lbs. friction And by the experiments on the level-as, 80 cwt. or 90160 lbs.: 2240 ::9.75:2:42 lbs. friction in a ton. The near coincidence between the results of the two sets of experiments, shows that the small inequalities on the rails of the inclined plane, which affected the small wheels, produced little or no sensible effect on the larger wheels. On the whole, it appears that the total rolling and axle-friction of Winans' 3-feet wheel-waggons, on clean rails, and at the velocities tried, is about 2 lbs. in the ton. The former remarks made on the oscillation and lateral friction will apply here, considering, as before, that the rolling and COAL-TARI axle-friction is not increased by an increase of velocity. It should be remarked that during the experiments, the waggons were tried with both light and heavy loads; and when gravity was the moving power, the waggons, with all weights, constantly passed over the same length in the same times. And former experiments have even shown, that a pair of wheels connected simply with an axle-tree, passed over equal spaces in equal times with a loaded waggon; thus clearly proving that the friction is directly as the load. In conclusion, it ought to be stated that no opinion is here meant to be given as the validity of Winans' patent, which is said to clash with one taken out by Mr. Brandreth of Liverpool. PLAN FOR DISPENSING WITH THE AIRPUMP IN THE CONDENSING STEAMENGINE. Sir, With a view to unfetter the condensing steam-engine by dispensing with the use of the air-pump, and, consequently, bringing the said engine to its natural perfection, the following project is proposed. Let the condenser be equal to the cylinder in area, and about 33 feet in length. A loose bottom, governable by a lever or pulleys, must close the under-end of the condenser at the starting of the engine. The injection-water will then accumulate until it ascends to about 31 or 32 feet (mineral water), when it will begin to preponderate, and the loose bottom will drop from the flange, and the condenser become a self-clearing condenser, effecting a pressure of 15lbs. per square inch at the top, acting on each side the piston alternately. The additional power and simplicity of an engine of the above construction are too obvious to require explanation. However, it may be added, that the water in the condenser is suspended as the mercury in the barometer, and its whole weight thus hanging, counteracts the pressure of the cylinder, and hence effects a self-clearing, and produces in the cylinder an uninterrupted vacuumnal power of about 15lbs. per square inch on each side the piston, as before stated. When the delivery-drift of 463 an engine-shaft is 5 or 6 fathoms below the surface, the situation is most favourable for the above construction. I am, Sir, Your most obedient servant, Shilbottle, near Alnwick, COAL-TAR, Sir-As from the great increase of gas-works, coal-tar is now produced so abundantly, it may be interesting to your readers to know that a most useful purpose to which it may be applied, has lately been discovered by a scientific person of my acquaintance, who has a house covered with red tiles, which were constantly requiring repair, either from the effects of frost, which shelled them off and gradually destroyed them, or from the wind, which blew them off the roof. He has covered them with two coats only of common coal-tar, laid on with a brush like paint, without the addition of any other substance. The first application was nearly absorbed by the tiles; the second formed a dark shining coat over the whole, resembling sheet-iron, and in a very few days became apparently as hard. The roof has since required no repair, nor has a single tile been affected by the frost; it appears to form one solid compact body, and rings, when I doubt not struck, as if it were so. the same effect would be produced on all roofing, covered either with tiles, Welch or other slates, or with the Oxfordshire Stonespild slates, all of which are liable, more or less, to injury from frost or wind. My house is covered with blue slates, and owing to the roof being too steep they are often blown off. As soon as the weather allows it, I shall certainly try the application. I am, Sir, Your constant reader, AN AMATEUR MECHANIC. COLZA OIL. Colza Oil, or Huile de Colza, is extracted from the grain of the Brassica Arvensis, or Campestris, a species of |