formed into rafts, and floated down the very rapid stream of the Reuss, by which the lake discharges its waters first into the Aar, and afterwards into the Rhine. By this conveyance, which is all of it in streams of great rapidity, the trees sometimes reach Basle in a few days after they have left Lucerne ; and there the immediate concern of the Alpnach company terminates. They are afterwards navigated down the Rhine in rafts to Holland, and are afloat in the German Ocean in less than a month from the time they descended from the side of Pilatus, a very inland mountain, not less than a thousand miles distant. We know not the amount of success which, in a pecuniary point of view, has attended the specu lation of Mr. Rupp; but, at one time, Bonaparte contracted for all the timber which he could send to the Rhine, and thereby prevented at least a stagnation of the commodity.

There are several scientific considerations connected with the facts now detailed, which seem to have puzzled Mr. Playfair not a little, and which, indeed, weighed with him so far as to make him refuse his consent to have his paper inserted in the Transactions of the Society, before whom it was read. The rapidity of the descent, so much greater than could possibly have been anticipated, is not he thought easily to be reconciled with the notions concerning friction, that are usually received even in the scientific world. It appears, however, that Professor Playfair was not familiarly acquainted with the most recent notions concerning friction entertained among practical engineers, and particularly with the fine experiments of the French writer, Coulomb: and consequently, whilst reasoning on the subject, hazarding his conjectures, and proposing his solutions, he was not aware that what appeared to him perfectly new, had been long received as established principles among men engaged in practical mechanics. It is pleasing, at the same time, to observe, that the inferences which the Professor draws from the facts before him, by means of mathematical reasoning, are substantially the same with those which experience has pointed out to less scientific persons; for the conclusions at which he has arrived, through a process of deep calculation, are found to coincide astonishingly well with the practical maxims of the ship-builder, when he launches a vessel from the slips, and with the operations of the engineer, in the movement of very heavy bodies on an inclined plane. In short, it seems to be now perfectly established, that heavy bodies when put in motion on an inclined plane, are relatively less retarded by friction than lighter ones are: and secondly, that friction, in all cases, is diminished in proportion as the velocity of the sliding is

increased. What the precise ratio is at which the friction is lessened relatively to the augmented velocity is, we believe, a point not yet clearly determined; but in regard to the fact itself, so little doubt is now entertained, that we are only astonished Mr. Playfair should have esteemed the announcement of it as a novelty in mechanics.

It is very true, however, as the Professor remarks, that we have here a strong instance of the danger of concluding in the researches of mechanics, from experiments made on a small scale, in regard to what should be the practice when applying the result to a large scale. When our experiments lead to the knowledge of a fact and not of a principle, there is the utmost caution requisite in extending the conclusions beyond the limits by which the experiments have been confined. And this is particularly the case with the experiments on friction, where we know only facts and have no principle to guide us; that is, we have not been able to connect the facts with any of the known and measurable properties of bodies.

"That friction belongs to the cases in which great caution is necessary in extending the conclusions of experiments, is indeed most strongly evinced by the operations that have now been described; the result of which is such as could not have been anticipated from these experiments. The danger here, however, is quite of an opposite kind from that which commonly takes place in such instances. The experiments on the small scale, usually represent the thing as more easy than it is upon the great, and engage us in attempts that prove abortive, and are followed by disappointment and even ruin. In the present case, the experiments on the small scale represent the thing as more difficult than when tried on the great one it is found to be; and would lead us by an error, the direct opposite of the last, to conclude things to be impracticable that may be carried into effect with ease. Had the ingenious inventor of the slide at Alpnach, been better acquainted with the received theories of friction, or the experiments on which they are founded, even those that are the best and on the greatest scale, such as those of another most skilful engineer, M. Coulomb, or had he placed more faith in them, he never would have attempted the great work, in which he has so eminently succeeded."

It appears however, in fact, that Mr. Rupp, the inventor of the slide at Alpnach, was much better acquainted than Professor Playfair with the received theories of friction, and in particular, we may be allowed to suppose, with the improved views derived from the ingenious experiments of Coulomb; and moreover, that it was because he had faith in the received theories, so modified and confirmed, that he engaged in the immense enterprise which is likely to hand down

his name to posterity, as one of the most enlightened engineers of the nineteenth century.

The volumes now given to the world as the Works of Mr. Playfair, contain his "Illustrations of the Huttonian Theory" the "Dissertation on Physical Science," published in the Supplement to the Encyclopædia Britannica; a variety of papers originally printed in the Transactions of the Royal Societies of London and Edinburgh; and, lastly, a selection from the articles which he contributed to the Edinburgh Review. The "Dissertation exhibiting a general View of Mathematical and Physical Science since the Revival of Letters in Europe," is worthy of the author's name; but unfortunately, owing to his death before the materials could be finally prepared for the press, it remains in an unfinished state, and must for ever continue in the shape of a mere fragment. As we intend to devote a separate article to it, in a subsequent number, we shall pass on at present to some of the minor pieces, which have not yet become known to the general reader.

One of the last things Mr. Playfair wrote, and with which he seems to have amused himself during part of the time he was confined with illness, is a Memoir relating to Naval Tactics, as improved by the late John Clerk of Eldin.

It is a singular incident in the history of human affairs, that a person who had never been at sea in his life, should have introduced into military seamanship the most important improvement which that difficult art has received in modern times. From his early youth, a fortunate instinct seems to have directed his mind to this line of study.

"I had," says he, in a document referred to by Mr. Playfair, "acquired a strong passion for nautical affairs when a mere child. At ten years old, before I had seen a ship, or even the sea at a less distance than four or five miles, I formed an acquaintance at school with some boys who had come from a distant sea-port, who in-` structed me in the different parts of a ship, from a model which they had procured. I had afterwards frequent opportunities of seeing and examining ships at the neighbouring port of Leith, which increased my passion for the subject; and I was soon in possession of a number of models, many of them of my own construction, which I used to sail on a piece of water in my father's plea. sure grounds, where there was also a boat with sails, which furnished me with much employment. I had studied Robinson Crusoe, and I read all the sea voyages I could procure."

Upon the commencement of the American war, Mr. Clerk, who continued to pay the utmost attention to the subject of naval tactics, and derived all the knowledge he could possibly

acquire from reading and conversation, and particularly from studying the details of the several actions which took place between the belligerents, saw more and more reason to suspect that there was something very erroneous in the method heretofore pursued by the British admirals, for bringing their fleets into battle. He perceived, that while nothing could exceed the skill with which the ships individually were worked and manoeuvred, the plan followed in bringing a whole fleet to meet the enemy was extremely uncertain and precarious: and, in a word, he was convinced from the conduct of our bravest and most skilful admirals, that an expedient for forcing their antagonists to fight, on equal terms, was an addition to the art of naval warfare that remained still to be discovered.

It had usually happened, that the British fleet was eager to engage, and that the enemy was unwilling to risk a general action; the object of our commanders, therefore, had almost always been to gain the weather gage, as it is called, of the enemy, or to place themselves to the windward of his fleet. When that fleet was drawn out in line, in the manner necessary for allowing every ship its share in the action, the British fleet bore down from the windward upon the enemy; who was so placed as to have his whole line, and also the broadside of each individual ship, nearly at right angles to the direction of the wind. In such circumstances, the British had usually adopted one of the two following methods, in order to make the attack. They either formed their fleet into a line parallel and directly opposite to that of the enemy, whence each ship bore down upon that which was immediately opposed to it; or, sailing on the tack opposite to that on which the enemy stood, ran along parallel to their line, and within fighting distance, till the whole of the one line was abreast of the other, and each ship ready to engage her antagonist.

If the former of these methods was pursued, each ship on coming down had to sustain a destructive fire from the broadside of the one immediately opposed to her in the enemy's line, which she could only return very ineffectually from the few guns mounted in her bows. The rigging, consequently, which presented the best mark, when the ship was moving end on before the wind, was in general so dreadfully cut by the enemy's shot, that the vessel was always much disabled, and sometimes rendered totally unmanageable, before she arrived within fighting distance.

If the second method was pursued, the headmost ship had to endure the fire of the whole line before she arrived in her place; the next, the fire of all but one; the third had to sus

tain the broadsides of all but two, and so on; so that it was very improbable that any, except the sternmost ships, could reach their station in the line without having received material damage. This mode of fighting, it requires not to be observed, would give to the enemy who remained quietly on the defensive, a great advantage over the attacking squadron, and enabled him almost to a certainty to maim his antagonist's fleet, with very little loss to himself, or even to gain a victory without exposing to any great hazard either his men or his ships.

"Mr. Clerk had the merit of pointing out the evils now enumerated, in a manner most clear and demonstrative, and of describing a method by which the attack might be made, without incurring any of the disadvantages that have been mentioned, and almost with a certainty of success. As the evil arose from an endeavour to diffuse the force of the attack, if one may say so, over the whole surface of the line attacked; so the remedy consisted in concentrating the force of the attack, and in bringing it to bear with proportionably greater energy on a single point, or a small portion of the enemy's line. For this purpose, the admiral of the attacking and windward squadron is supposed to come down, not in a line, but with his fleet in divisions, so as to be able to support the particular division destined to break through the line of the enemy, The consequence must be, that if this attack is directed against the rear of the enemy, the ships a-head must either abandon those that are cut off, or must double back either by tacking or wearing. Mr. Clerk shows, that if the enemy follow the first of these methods, and make his line either tack in succession or all together, such a distance must be left between them and the three or four sternmost ships, that not only must these last be easily carried, but that several more must probably be thrown into such a situation, as to subject them almost unavoidably to the same fate. If the enemy attempt the same thing by wearing, his condition will be still worse. The fleet by falling to leeward must not only desert the ships altogether, but must leave the sternmost of the wearing ships so much exposed, as to render it certain that they will be entirely cut off."

There can be no doubt that the system proposed and explained by Mr. Clerk was entitled to the full merit of origi nality. In his work he has entered into an historical detail which tends to establish this point, and in which, from the most authentic documents, he traces the plans of most of our remarkable naval actions, from that of Admiral Matthews, off Toulon, in 1744, to that of Admiral Greaves, off the Chesa peake, in 1781. In most of these actions we find, though con ducted by some of our ablest naval officers, that the British fleet being to windward, and by extending the line of battle