successfully with the mere mechanical skill and industry of other nations.

Michael Angelo has been the main topic to which I have been so bold as to claim your attention; and surely his position as an artist claims for him the respect and admiration of every painter, sculptor and architect. And although he was a great innovator in architecture, and introduced a license which was most pernicious to the art, yet we cannot but recollect that we owe to him the simplicity of design, to which he reduced the cupola and other decorations of S. Peter's, which had been sadly corrupted by the immediate successors of Bramante, whose original conception had been lost. Vasari mentions10 that "while Antonio San Gallo lived, Pope Paul had permitted him to continue the building of the Farnese Palace. But the upper cornice on the outside was still wanting; and his Holiness now desired that this should be added by Michael Angelo, after his own design and under his direction. The master, therefore, not willing to disoblige the Pope, who esteemed and favoured him so much, made a model in wood, seven braccia long (13 feet), and of the exact size which the cornice was to be. This he caused to be fixed on one of the angles of the palace, that the effect might be seen, when, as the Pontiff and all Rome with him were much pleased therewith, it was put in execution, proving to be the most beautiful and varied cornice ever erected, either by the ancients or moderns11. He continued the great court also, constructing two ranges of columns over those first erected, with the most beautiful windows, and a great variety of rich ornaments, ending with the great cornice; all of these works being so beautiful, that this court by the labour of Michael Angelo has now become the finest of all Europe."

12

You will doubtless remember the beautiful picture by Haghe in the New Water Colour Exhibition of the year 1848, representing Michael Angelo, himself an old man, nursing by his midnight lamp his faithful servant Urbino, who was ill; his master sleeping at night in his clothes beside him, the better to watch for his comforts. Vasari gives the following touching letter written to him by Michael Angelo on this occasion:

"My dear Messer Giorgio-I can but ill write at this time, yet to reply to your letter I will try to say something. You know that Urbino is dead, and herein have I received a great mercy from God, but to my heavy grief and infinite loss. The mercy is this, that whereas in his life he has kept me living, so in his death he hath taught me to die, not only without regret, but with the desire to depart. I have had him twentysix years, have ever found him singularly faithful, and now, that I have made him rich, and hoped to have in him the staff and support of my old age, he has disappeared from my sight, nor have I now left any other hope, than that of rejoining him in paradise. But of this God has given me a foretaste, in the most blessed death that he has died his own departure did not grieve him (so much) as did the leaving me in this treacherous world with so many troubles. Truly is the best part of my being now gone with him, nor is anything now left me, except an infinite sorrow. And herewith I bid you farewell."

I have been insensibly led, by the interest which attaches to the talents and character of this great man, to depart from the immediate subject of my paper, and to conclude my remarks by an allusion to his works at the Farnese, and by the contemplation for a moment of the affecting incident, which lays open the inmost soul of Michael Angelo, and shows him with the tenderest regard as a kind master, and the finest feelings of the most pious resignation in the contemplation of his own not far distant end, -as exemplary as a Christian as he had been eminent and admirable as an artist. But I will now conclude, and trust, that I may not be considered too presumptuous in so boldly offering my opinion as to the authorship of these architectural sketches. Whosesoever they may be, whether Michael Angelo's, or Vasari's, or any other artist's, they are extremely curious and interesting in the history of our art. I hope that none of my professional brethren, who have not yet seen these drawings, will now pass through Lille without visiting this fine collection. They will then, in addition to the delight they will experience in seeing the masterly thought-renderings of other great men, be enabled to judge for themselves and to decide, whether I am wrong or right in hesitating to attribute to the mighty Florentine these architectural sketches, which well deserve the minutest attention from every lover of architecture.

Discussion. Mr. TITE stated, that it happened to him, in the summer of last year, to be detained in Lille for five hours on a wet afternoon, waiting for the train to Calais, when he was directed to the Musée, in order to pass a portion of that time. Proceeding to the rather magnificent Hotel de Ville, described by Mr. Donaldson, of which he had never heard before, he was

10 Vasari's Lives, translated by Mrs. Forster, vol. v. pp. 296-7.

The cornice to the Strozzi Palace at Florence, must have suggested to Michael Angelo the grandiose character of that of the Farnese of Rome. 12 See Illustrated London News, 22nd July 1848.

astonished to find, not only the marvellous collection of drawings referred to, but an extensive and interesting museum, illustrative of art, antiquity, and ethnology. So easily might Lille be visited, and so well did the collection deserve further inquiry, that he strongly recommended his hearers to go there. In reference to the architectural portion of the drawings, he was sorry to find that Mr. Donaldson considered they were not, as he (Mr. Tite) had fondly hoped, the work of Michael Angelo. Mr. Donaldson had brought forward strong reasons in support of his opinion; and to his judgment and knowledge of the subject he must at once defer. He had himself copied from one of the drawings the name of Michael Angelo, which was clearly written upon it; and it would be very easy to compare that with his undoubted autograph, so as to settle the question. One of the largest of the drawings appeared to him to be the first sketch of the great architect for the dome of S. Peter's with the double cupola. He was informed at Lille that M. Wicar was employed by Napoleon Bonaparte in Italy to collect works of art, and that in doing so he helped himself to these drawings, which he bequeathed on his decease to his native city. In addition to the interesting letter of Francis I., which Mr. Donaldson had read, he begged to read the following from Bonaparte to M. Wicar, which was exhibited with the drawings; and which, notwithstanding certain peculiarities of diction, he had no doubt was dictated by Bonaparte himself, in 1796, from Milan :—

The sketches generally were singularly curious and beautiful; and he had been so much struck with them that he had contemplated interesting the architects of France with a view to have them published in lithography, which might be easily and cheaply done; and he would suggest to the Council that they might be able to promote this object. Whoever was the author of the sketches, he thought they might prove very useful in restoring the magnificence of ancient Rome. With regard to the Basilica of Constantine, he should be very glad to believe that there had been such a portico as the drawing referred to by Mr. Donaldson indicated. He believed, however, that both Palladio and Canina (the latter especially) were quite inclined to include a portico in their restorations of that building; but that it would be found that there could not have been such a portico, unless, indeed, the Via Sacra could be supposed to have passed within it. Institute were under the greatest obligation to Mr. Donaldson for the attention he had given to the illustration of these works, which were undoubtedly the production of some very clever man, if not of the great maestro himself.

The

Mr. DONALDSON said, that he had intimated to M. Benvignat, who was a member of the Commission having the care of these drawings, that he was sure the Institute would be much pleased to have tracings of them; but that gentleman believed this would not be possible, inasmuch as the Commission had the intention of publishing them very shortly. It would, however, be desirable to express the interest which this Institute felt in the matter, with the view of promoting that result.

Mr. BELL, M.P., bore testimony to the extreme value and interest of the drawings, both in an architectural and artistic point of view. He had himself intended to revisit them, and prepared a paper on the subject; but he rejoiced, that in directing Mr. Donaldson's attention to them, he had insured its being much more ably done.

Newcastle Docks.-The plans and surveys for these docks have been made by Mr. W. A. Brooke, C.E., and Mr. John Dobson, architect, of Newcastle, and been deposited agreeably to standing orders. A dock of about twenty acres, with suitable basin, tidal basin, and locks, is projected, with a depth of 23 feet at the outer lock sills, and a width of 52 feet in the locks, for the admission of large steamers. A railway of about half-a-mile will effect a junction with the York, Newcastle, and Berwick Railway.

GREAT EXHIBITION SURPLUS APPROPRIATION.*

THE surplus funds of the Great Exhibition have, with a government grant, been applied to the purchase of an extensive site at Kensington, with the understanding that it is to be appropriated to buildings for the promotion of science and art. As yet no definite scheme for effecting these objects has met with acceptance. The formation of an industrial museum does not at present offer the means of occupying the area, nor does it present such attractions as to be likely to obtain a very large grant of public money. The erection of a palace of science, or a palace of the institutes, in which all the learned institutions should be united and provided with theatres, libraries, and museums, has met with little support from the members of the institutions, who prefer central situations to location in a remote part of the enormous metropolis. The removal of the National Gallery, likewise supported by residents at Kensington, and by persons keeping carriages, is too evidently suited to the convenience of the aristocratic classes, and so opposed to the convenience of the great body of the population, that it has been denounced instead of being allowed, as hoped by the promoters, to be carried into effect with little resistance. If the deportation of the scientific institutions to Kensington is opposed to the convenience of individuals in easy circumstances, and has met with determined resistance, the monstrous proposition of withdrawing an establishment especially devoted to popular uses, from the reach of the population, justly deserves severe reprobation. The National Gallery, while it is designed to assist in the education of artists, was certainly never meant for the delectation of the aristocracy, who have more valuable galleries of their own, from which the public are excluded. It was because the treasures of art in this metropolis, among the richest in the world, are-in a mean and narrowminded spirit, and in opposition to the moral obligations incumbent on the owners-withheld from the public gaze, and because the English public, deprived of the opportunities of cultivation, are behind the standard of our continental rivals, that the National Gallery was established as a free public institution for the cultivation of the taste of the masses. If, from gross mismanagement the space provided for this collection is now found inadequate, that is no reason for its removal to Kensington, beyond the reach of the artizans of the east and south, and of their wives and children. Were it proposed to be moved nearer to the abodes of those classes, that would be a proposition more in conformity with the spirit of the institution than to move it to a remote part of those very districts from which the artizans are most removed. The same objection exists to the establishment there of a great industrial museum. The site is about as appropriate as Bethnal-green for the courts of law, or Battersea for the Bank of England.

In all schemes as to public buildings there is now this circumstance to be borne in mind-that the conditions of sites in the metropolis have been altogether altered by the abolition of the window duties. An adventitious and artificial regulation caused an enormous space to be covered over with small houses, in opposition to the natural habits of the population; but, now that the obstacles have been removed, large buildings have been erected in the heart of the metropolis, either as offices or as residences in chambers, suites of rooms, or flats; and this must go on to that extent, that suburban building will be checked, the population will be concentrated within the interior, or, by means of the suburban railways, enabled to choose their sleeping places and family establishments wholly in the country, instead of the mongrel villas and cottages of the suburbs, having all the inconvenience of a town residence, with the remoteness of a country site, and without either garden ground for the children or green fields. As the Times has well pointed out, a large space in the inner ring, as it were, of the metropolis, otherwise valuable for building ground, is covered with miserable courts and alleys, which can be obtained at a moderate price; and, in the end, these will be exterminated, and space will be given for large dwellings and for public establishments.

There is no occasion to remove either the learned societies, or the National Gallery from the neighbourhoods they now occupy, as a class of improvements similar to those in Paris, nay, similar to

"Observations on the Expediency of Carrying out the Proposals of the Commissioners for the Exhibition of 1851, for the Promotion of Institutions of Science and Art at Kensington, rather by the Public themselves than by Government." (Submitted, by permission, to H.R.H. Frince Albert, President of the Royal Commission.) By HENRY COLE, C.B. London: Chapman and Hall. 1853.

Victoria-street and Cannon-street, will give sites as cheap as Kensington, if not cheaper, and much more accessible. Any appropriation of Kensington must be with due attention to the course of events; and this is a most unpropitious period for the establishment there of any institution which is to be readily acces sible; for, independently of what has been already stated, the admission of railways to the heart of the metropolis, and more particularly the recognition of suburban, have given greater advantages for the concentration of the population of the vast area within the old seat of business. It may, too, with truth be said, since the establishment of the railway system, that all England is a suburb of the metropolis, so far as the public collections are concerned, or any great celebration. The convenience of these visitants must, therefore, be consulted, by avoiding any out-ofthe-way place for a public establishment, unless of an exceptional character.

The state of affairs as to the Kensington site is, that the site has been obtained, and there are no funds to do anything with it, nor, as we have said, any sufficient scheme for the ap propriation of funds. Mr. Cole (Felix Summerley, C.B.), who was one of the persons connected with the Great Exhibition of 1851, as he still is with those who may be called its executors and legatees, has published a pamphlet, which he represents as being under the auspices of Prince Albert. The purport of this pamphlet is to recommend that the site shall be turned over to a joint-stock company, the operations of which Mr. Cole does not specify, though he states, in a dedication to Prince Albert, that he is prepared to do so whenever it may be considered necessary. Mr. Cole is the best judge of the propriety of this reserve and demand of confidence, which appears too close a copy of Sir Robert Peel in a memorable period of political emergency.

It is rather a strange testimony to Mr. Cole's impartiality as a witness, that he propounds strong statements against the efficiency of government management, though he has been long a government employee, having first held a clerkship in some office, and latterly, on the strength of his Felix Summerley productions, having the good luck to be put at the head of the department of practical art, with a very liberal salary. We have expressed very strong opinions as to the efficiency of government management and officials, but we are outdone by Mr. Cole, and we think he has drawn his case so strongly that we are not able to endorse all his statements.

Mr. Cole seems to think that a very large sum of money will be required, and that it will be advisable that the management, to insure responsibility and unity of action, should consist only of one person, or, at most, three persons. Mr. Cole seems to think the legislature or the government will never grant such powers, or repose such trust. Here we differ from him, for we think they will. With regard to one point he mentions, an Historical Gallery of Painting and Sculpture, we fully expect that the funds will be provided, and that a competent director will be entrusted with their disposal. If, however, Mr. Cole means that he, or some other of the Great Exhibition officials, is to be entrusted with an unlimited control over the very large expenditure of public funds for some undefined object, we think he is quite right in assuming that the Legislature or Executive will never countenance anything of the kind. It is, however, a misrepresentation that the Legislature will not liberally provide for our acknowledged institutions or grant extensive powers. The British Museum surely has no reason to complain of want of confidence. The Department of Education, although new, has already been largely endowed, and is allowed to dispose of its funds without parliamentary interference in details. The National Gallery and Schools of Design year by year receive further endowments. Kew Gardens, under Sir William Hooker, has become an establishment of which the nation may be proud; nor are we aware that Greenwich Observatory has any ground of complaint. Where there is a ground of complaint, it is not, as Mr. Cole alleges; for the legislature do liberally endow, and grant full confidence; but it is, that there being no proper minister of education or of the fine arts, there is too much power in individual departments, too little control over them; and the want of a systematic organisation, whereby neglected objects might be provided for, and the fullest results obtained from existing institutions. The expenditure of the government is lavish, and if Mr. Cole and his patrons can really make out a case for a useful institution, they will have no ground to complain of the measure of support.

A very strange position taken by Mr. Cole is that government bodies are much less prudent, and much less bold in the

application and expenditure of money, because the money is the property of the public generally, and each individual at all interested considers he has a right to give his opinion on the mode in which they ought to be employed. This he does not consider to be the case with the directors of a public company. Our readers, who are more conversant with these matters, will differ in opinion with Mr. Felix Summerley. The British Museum and National Gallery managers have certainly not troubled themselves about individual suggestions or public criticism; and joint-stock companies, as railway directors well enough know, are particularly open to the interference of their shareholders. Had the writer instituted a comparison between individual management and that of boards, government or joint-stock, he would have been able to speak of the superior energy of one as compared with the other, but his preference for a joint-stock company is not supported by the arguments he adduces.

Another strange plea of Mr. Summerley is, that the administration of the government boards is constantly undergoing inquiry, and he enumerates several boards. This he adduces as a proof of the suspicion under which they lay. He quite forgets that railways, banks, assurance companies, and other joint-stock institutions, have been quite as often the subjects of inquiry and legislation; and if he had a Great Exhibition Company, or a Great Exhibition Commission, it would be just as liable to inquiry on public grounds by the legislature. He has also a notion that directors are more liable to penalties for malversation than government officials, but he does not refer to any evidence or experience of his own on the subject, and the state of the law gives no countenance for any such doctrine.

Other circumstances on which Mr. Cole relies are, that in the middle ages the churches were not built by the government but by the people, and that of late, canals, railways, &c. are the results of individual enterprise. This has nothing to do with museums and galleries of art, which are not remunerative undertakings, nor have any religious or superstitious recommendations. Of course Mr. Cole brings in that successive governments declined to undertake a national exhibition of industry. and, as he says, would probably do so again, and that at no time did the government give much countenance or help to the Exhibition. The Exhibition of 1851 was an exhibition of charlatanism and puerility, with the smallest amount of practical results and with a large amount of scandalous jobbery for the glorification of a contemptible clique. The manufacturers of this country have no particular reason to be satisfied with a performance in which they were treated with neglect and foreigners favoured; and the government had so much trouble and so little satisfaction with the exhibition and its concoctors, that they will not very readily subject themselves to a repetition of it.

Mr. Cole makes a comparison between private institutions for promoting science and art and those of the government, and says that the latter always suffer by it, instancing the Tower menagerie and the Zoological Gardens, and forgetting Kew and the Royal Botanic Gardens, Regent's-park. He therefore advocates "self-supporting" institutions, forgetting that for educational purposes we want not "self-supporting" but free institutions to put us on a level with our French rivals and American brethren. In confirmation of his dictum he says it is characteristic of the people of this country, that they do not value so much anything obtained gratuitously as that which they pay for, which is directly in the teeth of evidence; and we need go no further than the British Museum for that. He further says that there is an increasing dislike of the large provincial towns to the monopoly in London of great institutions to be paid for from the general taxation. This is a misrepresentation. The provincial populations do not complain of the British Museum, the National Gallery, or national institutions, which are used as much by them as by the Londoners: but they do complain, and justly, that they have not local museums, galleries, and libraries, which a better organisation gives to continental towns.

On these various assertions Mr. Cole contends that the plans for Kensington ought to be realised with the same success as the Great Exhibition, and the Crystal Palace at Sydenham, and that a joint-stock company should be formed for such purpose, to whom the area should be assigned, the government having a right of buying the whole or a part of the buildings, and of buying free admission for the public. Mr. Cole's joint-stock company is to erect spacious and attractive buildings for exhibiting collections, illustrative of the progress of science and art;

the formation of the collections and "the execution of various extensive works conducive to popular improvement and recreation," -in fact, so far as we can understand, to be an opposition Crystal Palace Company. Besides giving the area, the government are to be invited to lend or present to the company the National, Vernon, and other public galleries and collections, and to "agree to pay a fair rental for the space occupied by them."

We cannot say that Mr. Cole has made out any case for the support of the legislature or executive government, by grants or enactments in favour of his scheme, for we do not think they should be engaged in a kind of Crystal Palace, Vauxhall, or Hippodrome, which should properly be left to other speculators. If Mr. Cole, the Crystal Palace directors, Mr. Batty, or Mr. Charles Kean, while catering for the public amusement, choose to promote the cause of education by classical or artistic illustrations, we are thankful to them; but we see no reason to subsidise Mr. Cole or his company to enter into rivalry with the proprietors of theatres and exhibitions.

If it be true that the Kensington scheme has failed, it might be advantageous to sell the land to Mr. Cole and his joint-stock company to erect glyptothecas, colosseums, Mount Etnas, panopticons, glaciariums, pantheons, and hippodromes, as they may think most profitable. The funds from the sale of the area may be applied to the extension of the National Gallery, the building of a new one, or the formation of an industrial museum.

PROPELLERS.

JAMES SPOTSWOOD WILSON, Patentee, Nov. 8, 1853. The inventor states, that the proper place for the application of the propelling force, to promote horizontal motion, is at the centre of gravity, and this, in other cases, is generally found true in practice as, for instance, in the paddle-wheel of the steamship, and the driving-wheel of the locomotive steam-engine-and the proper position in which to apply the force in order to produce the largest amount of horizontal motion in proportion to the power employed. He learns from many examples, both in nature and art, that such position is at an angle of inclination 45° from the horizon. But his principal reasons for adopting that angle with regard to marine propellers is in consideration of the fact, that water increases in force in an equal ratio with the depth, from which arises its mean resistance at that inclination, and that the mean velocity of a falling body is obtained in that inclination also. By causing the power to act in the line of the former at that angle, upward gravity will be brought into action at a corresponding angle downward, but at right angles to the former, the resultant of which will be horizontal motion. The outer end of the propeller-blade, from its greater rapidity of motion, passes through a greater space than the portions nearest to the axle, and therefore does not require so much breadth of blade. In natural examples, we find that the fastest swimmers among fishes have their tails divided into long tapering lobes, instead of one broad sheet, and the swiftest among birds have long tapering wings. In imitation of these models afforded by nature the patentee forms his propeller, and therefore terms it the "Wing Propeller," not only on account of its situation and form, but likewise to distinguish it from the screw-propeller, as it does not retain any portion of the spiral character.

The vibration experienced in screw-propelled ships arises from the unequal density of the water in which the propeller acts; the force opposed increases in proportion to the depth, and the violence of the vibration is in proportion to the velocity. By the application of the wing propeller in the angular position (as represented in the engraving, fig. 1), the vibration would be completely removed-in consequence, first, of their acting in the line of mean resistance, by which means the difference arising from density would be one-half equalised; and secondly, their blades being made tapering toward their outward extremities, the forces and velocities would be more equally proportioned to the different sections of the diameter. It will be seen by the engraving that the propeller represents a pair of revolving wings. At figs. 3 and 4 it will be seen that the descending wings D, D, act like those of a bird, nearly horizontal, but descending in the line of mean resistance; while the ascending blades E, E, rise in a nearly vertical position, and press backward at the same time in a manner similar to the action of an oar in rowing.

The manner in which the patentee proposes to make the wingpropeller suitable as an auxiliary power is according to the fol

lowing description. The propeller-shaft is traversed spirally by a broad screw-thread, on which the propeller (fig. 2) fits; while at work the action will keep it firmly down to the collar D;

it into the space h, and liberate the propeller. In applying the power, the patentee proposes using only one steam-engine for one pair of propellers by placing the cylinder thereof horizontally across the ship, level with and in a line with the centres of the two cranks B, B, figs. 3 and 4, and furnishing it with one piston and two piston-rods, or rather one piston-rod passing through the piston and out of each end of the cylinder, so as to act like a double engine by having each end connected with a crank-rod. Figs. 3 and 4 represent the mode of application, by comparing which with the modes in use may be observed the amount of machinery that would be dispensed with, and the smallness of the space that need be occupied by the engine. To increase the velocity of the ship under this arrangement, the propeller wings should be lengthened, the stroke of the engine

In ocean steamers the necessity for being able to back water is not great, and is likely to occur only when coming into or leaving port. The patentee would therefore prefer to avoid providing for that evolution rather than to encumber his apparatus with a complicated mechanical arrangement. Yet, that his auxiliary shaft and propeller may be as perfect as possible, he contrives to key the propeller to its place in so simple a manner that it may be secured or liberated in a moment. To effect this, he proposes making the screw-thread on the shaft considerably broader than the spaces a, b, c, d, e, between its spiral revolutions; then, by having a key-way running the full length of the screw on the shaft, and sunk about half-an-inch deeper than the spiral thread, and a corresponding way inside the propeller; also, the lower end of the key A, A, should be formed so as to make good the deficiency of the screw-thread when the propeller is at liberty to ascend, but having space f, at its lower end to allow of its being driven down so as to permit the portions of thread to pass across

FIG. 3.

B

the spaces a, b, c, d, e, as shown at g, g, by which means the propeller would be prevented from turning on the shaft. The upper end of the key should be furnished with a nut B, fitted in such a manner, that when being run on it, it would drive the key A, A, down, and on being drawn off it would draw the key with

FIG. 4.

shortened, and the diameter of the cylinder increased to compensate for loss of leverage in the cranks. But as regards engines such as are constructed in the paddle-wheel steam-ships, they may be applied by using bevil gear to connect the propeller and engine shafts, and to multiply the velocity to the required

amount.

Claims.-1. The peculiar form of the propeller-blades hereinbefore described and illustrated; 2. The exclusive right of fixing a shaft or rod on the sides of a ship or other marine vessel in an angular position, as hereinbefore described; 3. The connecting of these shafts or rods by cranks to the pistons of a steam-engine, the cylinders of which engine shall be laid horizontally athwart mode of lifting the propeller by means of a spiral thread or screw the ship, and have a piston-rod working through each end; 4. The encircling the shaft, as described.

ESCAPE WATER-VALVE FOR MARINE STEAMENGINES.

By ROBERT WADDELL, of Liverpool. [Paper read at the Institution of Mechanical Engineers.] THE horizontal engine has of late years become a favourite engine in the British navy, for the screw steam ships have the advantage of being better protected from shot than the vertical engine, as the horizontal engine can be placed in the ship entirely under the water line; the boilers are also kept as much under the water line as possible, for the same purpose. All boilers are liable to prime, but when they are confined in the height of steam rocm, they are more apt to do so, as in this case, and carry a considerable portion of water from the boilers into the cylinders along with the steam. Water in the cylinders has, no doubt, been the cause of more accidents to engines than anything else; and many cases occur of the bottoms of cylinders being forced out, pistons broken, piston-rods bent, and side-levers broken-all from the effects of water in the cylinder. This can easily be accounted for, from the great power the one engine has over the other when water accumulates in the cylinder; the two engines being connected together in right angles, if a few inches of water has got into one cylinder, which will prevent the piston from getting to the end of its stroke, the opposite engine will be near half-stroke, at which point it gives out the greatest power, as the piston and crank are travelling near the same velocity, while the piston of the first engine, from the position of the crank, is nearly at a stand; then the power of the second engine, exerted to compress