was taken to Washington, where the verdict was confirmed.

In 1824, Mr. Ogden purchased in New Orleans an engine which had been built by Murray and Co. from the same patterns that had been used in the one built for him in 1817. He had it brought to New York, and employed the West Point Foundery Association to set it up on board a vessel he had built for a tug-boat on the Mississippi. The work was done under his immediate and constant supervision; and among the men employed was Mr. Hall, of whom Prof. Renwick speaks as the person entitled to the credit of first ascertaining the practical result of using expansive steam.

We have here given, in the most concise form, the evidence upon which Mr. Ogden's claim is based: comment might have hidden the strong impress of truth it bears. We cannot but express our surprise, however, that his native country should have withheld a right that has been freely yielded to him in England. In the London Mechanics' Magazine for the year 1829, his pretensions are clearly and boldly set forth, challenging contradiction: they have remained uncontradicted to this day. A few years since, when the project of establishing a regular communication by steam between England and the East Indies was a prominent topic, evidence was given before a committee of the House of Commons by a number of engineers and scientific gentlemen, upon the various matters affecting the proposed measure. So strongly associated with the use of steam expansively was Mr. Ogden's name at that time, that he was called upon to give the results of his experience with it in marine engines, and also to furnish such other information respecting the navigation by steam of our rivers and lakes as the committee desired to obtain. Those who may feel enough interest in this subject to search for authorities, if they have not access to the Report of the committee, will find in the Edinburgh Review, Vol. LX, a very able review of it, in which a principal part of Mr. Ogden's testimony is quoted at length.

FRENCH PROGRESS IN STEAM ENGINE MAKING.

Lyons, August 8, 1842. Sir, I have been for the last eighteen years a constant reader and admirer of the Mechanics' Magazine, though, unfortunately, I do not sometimes receive it till two months after date.

To fill up the vacancy, I take in some French publications, one of which, entitled "Publication Industrielle des Machines Outils

et Appareils, par Armengaud ainé,” is a respectable journal, with well-executed drawings of machines of every description. In the Number of this work for the last month, there is rather a remarkable Report by the Academy of Sciences, on a communication by M. Clapeyron, "On the setting of valves of steamengines." Should you think the nearly literal translation of it which I subjoin worth insertion, it may help to give your readers some idea of the relative positions of England and France, in regard to steam-engine making, at the moment when France has so magnanimously resolved to be no longer tributary to England for machinery! The gravity with which the expansive system is announced by M. Clapeyron and his friends of the Academy, as quite a new discovery, is as amusing as it is instructive.

Report on a New Method of Setting Valves of Steam-engines, by M. Clapeyron, of Paris.

Constructors of steam-engines have long since found that it was advantageous to place their valves so that instead of beginning to open at the instant when the piston has arrived at the end of the stroke, they shall precede. the piston a little; this is effected by a slight modification of the valve. They likewise observed that this arrangement had the effect of shutting the steam opening some time before the end of the stroke, and thereby causing the steam to act expansively. Until lately, very little importance was attached to this last circumstance; the expansion being proportionally small, it was looked upon as the necessary result of the disposition destined to produce the before-named effect (opening the valve sooner.)

The intention of the author is to develope this last circumstance, which has been looked upon, till now, as a secondary effect, from which nothing useful was to be drawn. shows, by the most simple modification of the common apparatus, that the three following conditions may be satisfied :

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1. That the introduction of the steam may precede the end of the stroke a given quantity.

2. That the escape of the steam may precede the end of the stroke a greater given quantity.

3. That the expansion of the steam will begin at a given point in the length of the stroke.

M. Clapeyron gives a geometrical diagram, by the aid of which may be found, in an easy and simple manner, the dimensions of

the valve, and the position of the eccentric to satisfy these three conditions.

In consequence of this disposition, the escape opening will be shut before the end of the stroke, so that the steam at the atmospheric pressure, in a non-condensing engine, will be compressed between the piston and the valve, thereby absorbing a great quantity of power. This compression is in proportion to the expansion, and may at first sight appear to reduce the power of the engines greatly.

The author shows, however, that to do away with this loss of power, the space between the piston and the valve, at the end of the stroke, ought to be such, that the compressed steam shall be equal to the pressure in the boiler at the moment the valves begin to open.

This improvement was applied by the author, in the year 1840, to one of the locomotives on the Paris and St. Germain Railway, when, with a consumption of fuel scarcely equal to that of the most powerful English engines, it has, at the same speed, drawn 50 per cent. more load (!!!) This engine has been ever since in regular service, and still maintains its superiority (!!!)

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This new way of working by expansion, for which the author claims priority, has the advantage of not requiring any new chinery; it has been used in England for some time past, and will, no doubt, become general (!!!)

Note by the Editor of the "Industrielle."

The details of the system proposed by M. Clapeyron, to work steam expansively, consists principally in the construction of the valve, to which a greater quantity of lap is given than formerly. It has been applied, to a certain extent, to steam navigation, and will, no doubt, extend to land engines (!!!)

I might name many other inventions that are deemed new here, but which may be seen in some of the earlier volumes of the Mechanics' Magazine, published 10 and 15 years ago. It is really amusing to see an old acquaintance, who many years since passed before us in a threadbare coat, out at the elbows, appear once more gaudily dressed in a Parisian paletot, of the newest academic cut. Not that I mean to say that the above method of setting slides is either threadbare or out at the elbows. It is a very sound and good method, and has no other defect than that of being-not

THE CRANK QUESTION.

Sir,-When I perceive how completely your correspondent "M.," has avoided saying anything on the real points at issue between us, I do not wonder at the shifts he has been driven to, to try and fill up his last letter. He was evidently puzzled how to manage writing a make-believe answer, when he found himself unable to contend any longer for his former conclusions, about which he had been so confident; and hit upon the expedient of taking to his old plan, of groundlessly charging me with misrepresenting him; going, I am sorry to say, still farther now, as he does not scruple to ascribe to me assertions which I never made; for in the first place, Sir, he actually charges me with having alleged that he had abandoned as untenable his previous position, that there was a loss proved by his experiment; whereas I really asserted the very contrary, viz. that it appeared to me that "M." had so completely annihilated his own conclusion, "that I need scarcely have noticed it again had he not very coolly" "" told us that his argu

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ments were as sound as ever!" He also accuses me of giving "garbled extracts" of his papers; but he does not seem to understand what garbling means: to constitute a garbled extract, as I understand it, a part must be suppressed, which would qualify the meaning of that part which is given : but to say, that I have given garbled extracts, because I have not quoted enough of his letter, to let it be "seen that" he "contended for a loss of power equivalent to 20," is absurd in the extreme. Any body that wanted to see what he was contending for, might refer to his letter; the object was to refer to his facts, and draw from them a correct conclusion, and I used his own words to ensure correctness in the reference. there was no room for garbling here, for he cannot deny the correctness of the facts, viz. that (at page 259), he told us that the work performed was represented by the number 149, and at page 470, that the power expended (in this same case) was 135 only. What then, may I ask, have I done "unfairly" here? My object being from these premises, thus brought together, to show that there could not be the loss of power "M." contended for, in this case: and from these facts, when they were thus brought into juxtaposition, I did certainly presume that your correspondent would allow that there was no loss of power, as far as the case went; and, from his studied silence in his December letter (page 470), as to whether there really was or was not a loss shown by that experiment, I did undoubtedly, and do still think, that he felt himself unable to show the existence of any such. I know he contended that

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there would be a loss of power equivalent to 20, but that is very different from showing what there was; besides, his argument there depended upon a mere supposition, and, as a proof, was utterly worthless; so that instead of finding fault with me for not repeating it, he ought to have been obliged to me for passing it over so lightly; for what, Sir, do you suppose is the foundation of this argument which he guards with such jealous care? Simply this, an assumption "for argument's sake" (mark, to help out his argument, not to assist in arriving at the truth), "that 5 lbs. additional weight would be sufficient" (i. e. that 5 lbs. added to the 50 under the table, would be sufficient to draw the 37 lbs. weight 6 inches.) Truly this is a very convenient method of investigation; what a pity it is not a little more experimental! This conclusive argument was not, however, so unnoticed as "M." seems to think; for though I did not remark upon the method of it, considering that I could afford to pass by a minor fault, having so many greater ones to expose, yet I showed him the fallacy of supposing that either 50 or 55 lbs. could, by his apparatus, move the 37 lb. weight over the space of 6 inches; he seems, however, not to have apprehended this part of my letter, and perhaps I may have been a little too concise; I shall therefore touch upon this subject again. It appears that in the original experiment before the cross bar came against the stop d, the 50 lbs. weight (suspended under the table), moved 2 inches, the 37 lbs. weight on the table being carried by it the same distance; but that afterwards the 50 lbs. moves only 0.7 of an inch, while the 37 lbs. is carried 2 inches, so that one moves nearly 3 times as fast as the other, and is therefore acted upon at a mechanical disadvantage of nearly 1 to 3. Now if we suppose, as "M." assumes, that the 5 lbs. added to the 50 would cause it to move 4 inches (in its whole course) instead of 2.7 inches; then, previous to the bars coming against the stop, both the weights will have moved 2 inches, and the quantity moved by the 37 lbs. afterwards, may be ascertained by the following proportion, 0·7: 2 :: 2 : the required distance, which will therefore be equal to 5.7. Adding to this the 2 inches moved previously, we shall have the entire distance traversed = 7.7 inches, and consequently the work done =37.3 x 7.7=287.2, while the power expended would be only, according to 'M.'s" own showing, "55 x 4 = 220." If then, Sir, your correspondent's expectations had been fulfilled here, I say, as I said before, his crank must have increased the power instead of diminishing it.

If any of your readers, Sir, have taken the trouble to observe how regularly I have can

vassed and refuted every statement of "M," and how he has scarcely ventured to bring forward again three or four out of twelve or fifteen objected to, and has not even succeeded in establishing one of these, it must appear to them ridiculous enough to have him accusing me of "beating a retreat," and hinting that I was hard pressed! (By whom, I wonder?) And charging me with pretending to misunderstand him, when I find it more convenient to do so than to refute his arguments !

There is one thing, however, that I perfectly agree with "M" in, viz., that "it is very necessary" for him "to explain, in language that cannot be misunderstood, what" his "meaning of the term, loss of power, is;" this he professes to do in his last letter, but nowhere, in the whole of it, can I find the smallest explanation in lan. guage on the subject. He attempts to exemplify what it is, but does not make the least attempt to define his meaning. His exemplifications, too, are curious enough. He supposes a case of two engines, one rotative, and the other a crank engine, and then tells us, that if the one is found to do more work than the other, then there is a loss of power in the crank; and that this (what? this loss of power?) is clearly the meaning of the term loss of power. This puts one in mind of Bardolph's definition—

"Accommodated? That is, when a man is, as they say, accommodated: or, when a man is,being, whereby, he may be thought to be, accommodated; which is an excellent thing."

Your correspondent is evidently determined not to commit himself by an explanation, though he talks so big about giving one, requesting me to be as explicit as he is ! He will not even say how far he agrees "loss of with my definition of the term power;" and really I don't know how I could be more explicit than I have been. Either there is a loss, owing to the crank, or there is not; if there is a loss of power, it must be irrecoverable, otherwise it is not lost; but if it is recoverable by any contrivance, then it is not lost, and then, therefore, there is no loss; there may be a mechanical disadvantage which is neutralized by that contrivance; but, that a mechanical disadvantage is not what he means by a loss, "M." has allowed in one of his former letters.

Your Aberdeen correspondent, "A Mechanic," mentioned some time ago, (vol. xxxiv. page 439,) an experiment comparing a rotative with a crank engine, and stated that the power of the former had been found "much greater, nearly double" that of the latter, and then proceeded to show why it was so that if the crank-engine had raised

the same weight, it would have done so with a greater velocity, and therefore that the effective power of the engine would have been increased; so that we should have had more work done by the crank engine than by the other, if they had moved equal weights. "M.'s" representation of this case is like some of his other representations, which illnatured people would be apt to call misrepresentation, and exaggeration too; for, instead of saying that one engine had nearly double the power of the other, he says that your northern correspondent admitted that the crank engine did not do one half the work of the other! If" M." can give us no better example of loss of power than this, I fear his boasted loss will dwindle down to be no more nor less than a mechanical disadvantage; the existence of this, in part of the crank's course, nobody will deny, and it is evidently all that is exhibited by "A Mechanic's" experiment.

A curious mental hallucination seems to have taken possession of "M.," in part of his letter, where he attacks me about "friction," particularly in the following sentences. Telling us of the friction of drawing a spike out of a piece of timber, he says, "but your correspondent cannot dispense with the friction of the spike;" and again, "now, your correspondent is disposed to turn round and cavil with me about this friction, on the ground of a misunderstanding about words, and that this friction was excepted." Now, Sir, would you believe, if you had not read my letter, that in no one part of it, from beginning to end, did I once mention friction, or even allude to it directly or indirectly, except where I remarked upon the well-known elementary law of friction, the truth of which "M." denied.

These friction notions "M." seems (from what he says) to have extracted by some new process (worthy of being patented, as it discovers things which have no existence) from some observations I made on the action of a fly-wheel, saying that some work could not be well done without it; but what has this to say to friction? The case is the same, whatever the work consists of, if it is uniform: he objects that in this case my crank will not move without momentum. Who said it would? I am sure I never did: I know it cannot: but, when we give it the momentum with a fly, and find that the work is done, what reason have we to suppose that power has been lost? The fly acts as a reservoir, receiving, and as it were laying up in store, the overplus power at certain points, where the force exerted is greater than what is necessary to perform the work; giving out its store at other points, where the force exerted is not sufficient to perform the

work

anything that would perform this office would answer just as well as a flywheel. In a steam-boat where two engines are used, with cranks at right angles, no momentum is required: does "M." contend for . a loss there?

From what " M." says here, he seems to agree in considering the fly-wheel as an indispensable addition to the crank, and an assistance, but in a former letter he told us that it was the cause of an additional loss ! -which however he has never attempted to show.

Your correspondent is very fond of alluding to the doctrine of virtual velocities, but he never goes any farther: he tells us that if it applies to the crank, it must also apply to his experiments; thus pretending to answer an objection, which nobody ever made (by the bye, this is a sophistical method of replying, which he is growing too fond of, and has made use of in several parts of his letter.) In one of my first letters I told him that there was nothing in his experiment at variance with this doctrine, and he has never attempted, before or since, to prove that there was.

As to his non-momentum experiment, I do not consider it necessary to make any reply to what he says on that subject in his last letter, for he has not been able to answer the two objections in the sixth paragraph of my last letter (p. 76), the latter of which puts him in the dilemma of either showing that he does not understand the action of the spring in his own experiment, or, that the loss he talks of is only apparent, not real, and has nothing to do with his crank.

There are several minor matters in "M.'s" letter scarcely worth notice; but I may just remark, that if I did say (as he has quoted),

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get a suitable apparatus and it can be done," I did not mean, "take away the crank;" I should rather have said, Keep the crank; but suit it to your work. Well might "he" wonder if he thought I was in earnest, at my calling the power lost, where it is capable of being reproduced; I should have put a note of admiration after lost, and then perhaps he would have understood that I called it so ironically, to show the absurdity of his believing in such a contradiction. Why does not 74 x 3 answer the conditions? I had as much right to use "M.'s" argument in finding what weight should be carried 3 inches, as he had in finding the same for 6 inches. My addition to "M.'s" apparatus would not in any way meddle with his crank, but I have not time or space to give it now.

And now, Sir, concluding this letter as I began my first, my object being still to show "M.," that there is no loss of power in the