These trials were made at the works of Messrs. Nasmyths, Gaskell, and Co., Patricroft, near Manchester. They were conducted in the presence of a member of their firm, of their superintendent, Mr. Wilson, and of two of the patentees of the Disc Engine.

The object proposed being to ascertain, with the utmost possible accuracy, the relative quantities of water as steam, and, consequently, of fuel, which would be required to enable each engine to perform the same amount of work, it was a matter of the first importance to determine upon some work which would oppose an uniform resistance. after much consideration, I selected that which is presented by fans revolving at high velocities; considering that these machines, when driven at an uniform rate of motion, would offer a resistance so nearly invariable as to satisfy this primary condition. The Christmas holidays fortunately admitted of fans being appropriated entirely for this purpose, so that no extraneous circumstance interfered to change the nature, or amount, of the work during the trials.

The Reciprocating Engine was made by Messrs. Nasmyths, Gaskell, and Co. It is a beam engine, thoroughly well constructed, in excellent condition, and in every respect unexceptionable as a specimen of its class. I found the diameter of the cylinder to be 14 inches; the length of stroke 2 feet, 24 inches; and the number of double strokes of the piston, during the trial, averaged 41 per minute.

The Disc Engine (called 16 horses' power) I found to have a steam chamber of 27 inches in diameter, and the mean number of revolutions effected, during its trial, was 118 per minute. With these proportions, and at these respective speeds, the volume of steam which should pass through each of the two engines in a given time, as defined by the transit of the parts on which the steam acts, is very nearly the same; an equality which must be considered as tending to satisfy doubts as to the results of the trials having been affected by any other circumstances than those strictly arising out of the principles on which the two engines are constructed.

Both engines were alternately supplied with steam from the same boiler. This I found to be very deficient in the extent of surface exposed to heat, and the setting was ill arranged; consequently, the proportion of water evaporated for the coal consumed was low; but, as I adopted on this, as on former occasions, the mode which is considered to afford the only accurate means of ascertaining the expenditure of steam for a given effect, viz., that of determining the consumption of water as steam, the results

obtained are free from all question which might otherwise arise as to the capability of the boiler, or the quality of fuel made

use of.

The two engines, being thus supplied with steam under identical circumstances, were employed, on alternate days, to drive the same fans at similar velocities.

It was found, by previous trials, that with the quantity of steam the boiler would conveniently produce, the Disc afforded a greater amount of power than the Reciprocating Engine; therefore the number of fans driven, their velocity, and the discharge of air, were so adjusted as to provide for the resistance being within the capability of the latter engine; and thus I was enabled to keep the fans revolving at a very uniform velocity throughout both trials. This velocity was accurately indicated by a counting apparatus connected with an intermediate shaft between the engine shaft and the fans.

The two engines were of the non-condensing class, and discharged their steam into the atmosphere.

For the registration of the water a vessel was provided, which was found to contain 338 lbs. by weight; and it was arranged for the whole of the water used during the trials to be measured by means of this vessel; and the boiler being furnished with a glass gauge, I endeavoured to have the same pressure of steam, and the same quantity of water in the boiler, at the conclusion, as at the commencement of each experiment. In this I succeeded within a variation of an inch in the level of the water, for which due allowance was made.

The weight of coal burnt during each trial was also accurately ascertained; the fire at the conclusion being, as nearly as possible, in the same state as at the commencement.

Having thus taken the precautions I considered requisite to obtain results worthy of confidence, and having made some preparatory trials with each engine, the fans were connected with the Reciprocating Engine and they were driven without intermission for six hours. During this time the quantity of water as steam which passed through the engine was 10,406 lbs., equal 1734 lbs. per hour; and the coal consumed was 20 cwt., equal 373 lbs. per hour; the evaporation being in the low ratio of 43 lbs. of water for 1lb. of coal. The counter actuated by the intermediate shaft registered during this trial 14,301, the greatest difference in the velocity of the fans during any hour being about 6 per cent., and the mean speed of the engine 41-6 strokes per minute.

On the following day the fans were connected with the Disc Engine and driven for 5 hours and 57 minutes, when the counter, connected as before, had registered 14,318,

being 17 more than on the previous day; the greatest difference in the velocity of the fans during any hour being little more than 1 per cent. The quantity of water as steam required to supply the engine was 8,697 lbs., equal 14494 lbs. per hour; and the coal consumed was 16 cwt., equal 298 lbs. per hour; the evaporative ratio being about 44 lbs. of water for 1lb. of coal. The mean number of revolutions of the engine shaft per minute was 118.

Immediately after the conclusion of this trial, the fans were again connected with the Reciprocating Engine, and the same velocity being given to them, an indicator diagram was taken off which, by comparison with the diagrams of the preceding day's trial, showed that the resistance overcome by the Disc Engine, was somewhat greater than by the Reciprocating Engine, but the difference was very small,

In order to ascertain the amount of effective power exerted by the Disc Engine, I availed myself of Mr. Davies' Dynamometer. The principle of this very complete instrument is, that the force of the resistance taken on the periphery of a driving drum or toothed wheel on the engine shaft, is denoted on the dial-plate of a spring balance, so placed that its index may be easily observed whilst the engine is at work. The engine being stopped, standard weights are suspended from the drum or wheel until the index of the spring balance marks the same degree at which it stood on the dial-plate during the action of the engine; and the velocity and circumference of the drum or wheel in feet being also known, true data are obtained for determining the work performed. By means of this apparatus-which I consider to be worthy of the utmost confidence I found the mean resistance, or load, actually overcome, to be equal to 17 horses' power. Although this instrument was applied only to the Disc Engine, yet as it defined the resistance overcome by each, it indicated with equal truth, the effective power exerted by the Reciprocating Engine. The Dynamometric observations were further corroborated by the diagrams obtained on applying the ordinary indicator to the Reciprocating Engine, when driven without a load and when performing the same work. The indicator was verified by comparing the pressures marked by this instrument with those of a mercurial gauge acted upon by steam at various densities. The quantity of water as steam required by the Reciprocating Engine being 17343 lbs. per hour, and the effective power exerted equal to 17 horses, the water consumed is in the ratio of 102 lbs. for each horse power, per hour; and the water required by the Disc Engine being

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1449 lbs. per hour, this is in the ratio of 85 lbs. per horse power per hour. Thus, the consumption of steam, and consequently of fuel, for equal effect, by the Reciprocating, is upwards of 19 per cent. greater than by the Disc Engine.

The mean pressure of steam in the cylinder of the Reciprocating Engine, as exhibited by the indicator diagrams, was equal to 25 lbs. per square inch, and the mean pressure in the chamber of the Disc Engine, as exhibited by a mercurial gauge constantly connected with it, was 234 lbs. per square inch.

sures.

The above effects were obtained by the two Engines when working unexpansively and with steam at comparatively low presAs regards non-condensing Reciprocating Engines, I have not previously met with any (and I have conducted experiments, similar to the foregoing, on many engines of this class) which has required less than 120 lbs. of water as steam per horse power per hour, even when using steam at high pressure, a fact which establishes the excellence of the Reciprocating Engine subjected to trial, as it only consumed 102 lbs. per horse power per hour.

The results of these trials are thus exhibited in terms of the quantity of water as steam actually expended in overcoming the same resistance by the two engines, and, also, according to the conventional phrase of horse power; but that quantity was greater in both cases than would have been required, had the steam pipes and cylinders been coated. Though, however, these were uncovered and a considerable quantity of steam must have been condensed, which had no share in producing the effect, the relative results are unaffected by this circumstance, as I found, that a nearly equal extent of surface (about 45 square feet) was so exposed in both cases.

When experiments of this kind are conducted in a manner liable to little error, evidence of their accuracy will arise from independent sources, and we possess direct means of verifying the correctness of the principal results obtained, viz., that the Reciprocating required 19 per cent. more steam than the Disc Engine, for equal effect.

The counter informed us that the Reciprocating Engine made in the 6 hours 14978,4 double strokes, which multiplied into its capacity* (passages, &c. included) gives a total of 78,726,4 cubic feet, as the volume of steam which passed through the cylinder at the absolute pressure of 40 lbs. per square inch. The ratio of the volume of water contained in that steam is as 1 to 677.

The passage equalled 0-405 cubic feet.-Total capacity, 5,256 cubic feet.

The capacity of the Disc Engine* was also exactly ascertained; it was filled and evacuated 42,322 times during the 5 hours and 57 minutes; and the total volume of steam expended amounted to 69,535 cubic feet, having a mean absolute pressure of 38 lbs. per square inch, for which the ratio of the elementary water is as 1 to 710. By comparing the quantities of water given by this method of computing the respective consumption of each engine, it appears that the Reciprocating would necessarily require 184 per cent. more water than the Disc Engine, which confirms the correctness of the two experiments.

There are still a few points which I feel called upon to note, as they affect, to a certain extent, the results of the trials.

and

The Disc Engine was quite new, therefore its acting surfaces were not in that high state of polish I have seen in those which have been in constant use for many months. Thus somewhat more power would be consumed in overcoming its own friction in this case, than in older engines. On the contrary, the Reciprocating Engine had been at work for a period which had brought its rubbing surfaces into a perfect state. The Disc Engine, also, was planted, temporarily, on the wood floor of an upstairs room being simply bolted down to sleepers; and the manner in which the driving strap was obliged to be rigged, for the purpose of the trial, increased the friction of the engine shaft on one journal. Though the practicability of such an arrangement exhibits a property of much importance to the employers of engines, viz., the small mass and cost of foundation necessary for the Disc Engine, yet, it is unquestionable that the circumstances referred to were adverse to this engine in a comparison as respects economy.

I have already alluded to another circumstance which was adverse to the economy of both engines, viz., the surface of steam pipe, and &c. exposed to the influence of the air in the building, and amounting to about 45 square feet. By experiments on a large scale, and pursued for a lengthened period, which I have made with steam under similar circumstances, and at similar pressures to those used on this occasion, I have found that 1 square foot of cast-iron pipe will condense fully 1 pound of steam per hour. Thus, about 270 lbs. of water should be respectively deducted from the consumption of the Disc and Reciprocating Engines, as those quantities had no share in the production of the effect. Making this deduction, it comes out that the effective horse power was really obtained with 82 lbs. of water

• Disc capacity, 1-643 cubic feet.

as steam, per hour, by the Disc Engine, and with 99 lbs. by the Reciprocating Engine. In concluding this statement of the results attending an investigation alike interesting and valuable, as regards the practical facts elicited, I must express my entire confidence in their accuracy, checked as my observations were throughout by so many competent persons, all of whom were most diligent in guarding against error during both trials. I am not acquainted with any experiment in which the same load, without the slightest change in any part of the intermediate gearing, has been made the medium of deciding on the comparative merits of different steam engines; and had I to choose again, I do not think a resistance could be selected subject to so little variableness as the fans adopted on this occasion. This kind of resistance offers peculiarly accurate means of noticing the quantity of irregularity occurring in the speed of any engine. The uniform velocity obtained by the Disc Engine was very apparent, and struck me as a property of no small importance as regards its application to various purposes, for which an equable rate of motion is a desideratum.

I am, Gentlemen, your obedient servant,
JOSIAH PARkes.

(Signed)

HAY SWEEP.

J. P.

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the right, and the other to the left, to guide their horses; but I think, if there was a sufficient weight attached to, or fixed on each end, that there would be no occasion for any one to stand there;

the horses might then be led by even two boys.

I think this would be an exceeding useful machine in all moderately level pastures, and, although it has been used for many years in the north of England, I never saw it elsewhere.

I remain, Sir, your obedient servant,
M. S. R.

Description.

This machine should be made of oak, except where the uprights, a a a a, are, and those (four) should be of iron; the bottom parts, with flat or round heads, let in neatly, so that the bottom should be quite level, and the tops fastened by screws and nuts.

The top and bottom rails are 4 inches by 3, or 14 inches circumference. Length of the back or centre part 8 feet; ditto of each side or wing 4 feet 6 inches; depth all round, 3 feet 6 inches. The two sides, or wings, are so fixed as to move backwards or forwards by turning on the outward iron bars, which pass

through holes, thereby affixing the wings to the centre. These iron bars should be round.

A strong rope is interlaced through the rails near to the bottom, and that is connected with the top by a smaller rope; and at each end is a splinter bar A A, to which a horse is affixed.

This machine is of great service in catching weather, when your hay is nearly made, and when to prevent its being wetted by sudden rain, you wish to get it up in large cocks. The present plan to accomplish this, is by the men pushing it up with forks, but by the machine more may be got up in one hour than many men would be able to do in a day.

Where the rick is made in the same field, or in one of several hay fields adjoining each other, the time and trouble of carting is saved, for, by this machine it may be drawn up at once to the place where the rick is to be made, and only two horses are required.

by the commander of the Geyser, Capt. Carpenter. The advantage expected from having the pinnace thus equipped was, that she might be able to tow the other ships' boats, against wind and tide, into shallow harbours and rivers where an armed force might be wanted, but which the vessel herself could not, from her draught of water, penetrate. Two trials of this auxiliary pinnace steamer were made last week on the Thames, in the presence of Sir Edward Parry, Comptroller of Her Majesty's Steam Marine, and Messrs. Ewart and Lloyd, the Government Engineers, and the result, as reported to us, was in the highest degree satisfactory. The pinnace is 30 feet in length, 9 feet wide, and is capable of carrying 8 tons. She is remarkably bluff in the bows, and therefore not adapted for high velocities; but power (a little power only) and not velocity, is what is aimed at in the present instance. The disc engine with which she is fitted weighs altogether but 6 cwt., and measures 3 feet by 1 foot 6; leaving ample space for a full complement of men. The connexion between the engine and the propellers (of which we gave a full description in our No. 844, p. 18) by means of grooved pulleys, and catgut bands. During the first trial, a regular speed of 7 miles per hour through the water was obtained, as indicated by Massey's log, although from the unfavourable shape of the boat, a wave of nearly 18 inches deep was carried before the bows. The velocity of the engine-shaft was 200 revolutions a minute, and more than that is not, we understand, desired from the propelling shafts. In the second trial, the pinnace drew after her at about the same rate of speed, a regular gun-boat, furnished with cannon, and a complement of fifty men, with their arms and ammunition. The engine and boiler are so fitted to the pinnace, that they can be taken out in five minutes, and replaced ready for operations in the same brief space of time.

WALKER'S HYDRAULIC ENGINE. Sir,-Walker's hydraulic engine is deservedly attracting great attention, and the better it is understood, the more it will be admired. Your last Number (975) contains three papers, in two of which Mr. Walker's invention is adverted to rather disparaging ly. The first is a rival, (S. P.,) who favours us with a modification of the "powder puff pump" of the sixteenth century. spiral wire, tube of mackintosh cloth, or of leather," bespeak the ephemeral character of such a machine, and stand little chance with a competitor which threatens to last almost for ever-and a day. "S. P." has seen Mr. Walker's machine, but from the con

"The

cluding paragraph of his "description," he evidently has not yet mastered its modus operandi.

Mr. Tozer (page 315) endeavours to prove a want of novelty, by bringing forward the contrivance of a Mr. Wood. Mr. Walker's Belgian patent was at first refused in consequence of a supposed resemblance between his contrivance, and that of Mr. Wood; on examination, however, the two inventions were found to be dissimilar, and the patent was passed.

It is not at all probable, if this excellent mode of raising water had been once hit upon, that it would ever have been lost, though we are told, by the by, that the thing is a perfect fallacy;" so saith Mr. A. Emslie, at page 315.

That it is perfect, I will not assert; that it is no fallacy has been incontrovertibly proved. I have watched the progress of this invention from its first germ to its present maturity, and Mr. E. might have been contented to take my description, or to bring against it the result of some practical experiment. Mr. Emslie says, "The lift does not discharge the water," and upon that reasoning he builds his hypothesis of the similarity of Mr. Walker's engine to a lift and force pump. The fact is, the lift does discharge the water! This is seen plainly enough in filling Mr. Walker's glass elevators; it is also shown by naking the down stroke so slowly as to be inoperative, when the up stroke performs its own peculiar office. The fact is also shown by filling the elevators, and removing them from "the water in the well cistern, or what-not," when their contents are still delivered without any aid from the "consequent resistance."

Mr. Emslie further says, "I defy Mr. Baddeley to show that this weight of water is in any way counterbalanced by the other elevator, while in action." Mr. Emslie's defiance will not induce me to undertake the part of showman; but Mr. Walker has shown to thousands, and, I dare say, will show to thousands more, that which Mr. Emslie cannot comprehend. The mode of demonstration resorted to by Mr. Walker, is simply to detach one of the elevators from the beam; on working the machine, the quantity of water then raised is just onehalf, but the labour is nearly doubled! On refixing the elevator, and working the machine, the quantity of water is doubled, and the labour reduced as before, affording the most unequivocal proof of the advantages of the equilibrium to which I alluded in your 971st Number.

Mr. Emslie may depend upon it there is more in Mr. Walker's hydraulic engine than was ever dreamed of in his philosophy, and