"I" (No. 301) appears to have rated the superiority of the camera lucida over "the unwieldy construction of bars, joints, and pullies," rather too high. Query. Does “I” understand the use of the pantagraph? The camera lucida may be a very clever instrument for copying views, &c.; but is it capable of reducing plans or drawings to any required proportion? I have never seen one, nor can I meet with a drawing of it in the encyclopedias, which take but slight notice of it. Perhaps "I" or some other correspondent could furnish a drawing and description.

MUSCULAR STRENGTH.

Borellus was the first who demonstrated that the force exerted within the body greatly exceeds the weight to be moved without, and that nature, in fact, employs an immense (we had almost said superfluous) power to move a small weight. It has been calculated that the deltoid muscle alone, when employed in supporting a weight of 50 pounds, exerts a force equal to 2,568 pounds. Some notion of the force exerted by the human body in progressive motion, may be formed from the violence of the shock received when the foot unexpectedly impinges against any obstacle in running. The strongest bones are occasionally fractured by the action of the muscles. The muscular power of the human body is indeed wonderful. A Turkish porter will run along carrying a weight of 600 pounds; and Milo, of Crotona, is said to have lifted an ox weighing upwards of 1000 pounds, Haller mentions, that he saw an instance of a man, whose finger being caught in a chain at the bottom of a mine, by keeping it forcibly bent, supported by that means the weight of his whole body, 150 pounds, till he was drawn up to the surface, a height of 600 feet. Augustus II. King of Poland, could, with his fingers, roll up a silver dish like a sheet of paper, and twist the strongest horse-shoe asunder; and a

prodigious power of the muscles is ex hibited by fish. A whale moves-with velocity through the dense medium of water, that would carry him, if continued at the same rate, round the world in little more than a fortnight; and a sword-fish has been known to strike his weapon quite through the oak plank of a ship.

MISCELLANEOUS.

Printing as Rapid as Writing.-We have examined a curious inachine invented by Mr. Bart, of Macomb county, called by him a typographer. Its object is to enable a person to print with the same rapidity with which he can write, and to make one or more impressions, at the same time, to the number of twelve. The letters of the alphabet are stereotyped together in a curvilinear groove, and affixed to a rod, one end of which moves upon a swivel, and the other is held in the hand. An index is immediately before the eye of the operator, where the letters are also arranged, and a notch corresponding with each letter is cut in a brass plate. The paper to be printed on is passed over a bar with a proper edge, covered by a cloth, and is moved by a rol ler; and the person operating has only to put the rod in the notch corresponding with the letter which he wishes to print, and the impression is made. The elevation of the rod from the notch inoves the paper just far enough for another im pression, and so on till the work is complete. The downright movement not only makes the! impression, but keeps the types sufficiently provided with ink. The operation is as rapid as writing, and far less fatiguing. The machine is not less curious for its mechanical ingenuitythan for its admirable simplicity. Bishop Wilson said, that the time would come when a man preparing for his journey would call for bis wings as familiarly as for his boots. We have no doubt but the time is near when a man, to prepare his epistle, will instantly resort to his typo grapher, instead of his pen and ink.-American

paper.

Malleability of Platina-When a piece of platina is heated in a furuace, great care should pe taken that no part of it is exposed to the blast in the chimney; for that part immediately loses its primitive malleability, and becomes as brittle as zinc.

INTERIM NOTICES.

The Editor being absent from town, attending the Locomotive Engine competition, of which some account is given in this week's Number, he requests his Correspondents will rest satisfied with a general acknowledgment of their favours till his return...

Communications received from KappaHenry D-A Constant Reader-Mr. Saul-Mr. Woollgar-J. N.-A Private Teacher-Mr. H. Guerr-Mr. J. Gilbert-Mr. Chapman-T. R.J. B.-Mr.James Harrison.

LONDON: Published for the Proprietor, by M. SALMON, at the Mechanics' Magazine

have left the impression of his teeth upon a piece of solid ron. The most

nications for the Editor (post paid) are requested to be addressed.

M. SALMON, Printer, Fleet Street.

COMPETITION OF LOCOMOTIVE CAR-, RIAGES ON THE LIVERPOOL AND MANCHESTER RAILWAY.

In our last Number we gave an account of the commencement of this interesting and important competition, drawn up on the spot, between the closing of the first day's proceedings and the departure of the post, and necessarily therefore both brief and imperfect. We now propose to resume the subject de novo, and to go into it with all the fulness and circumstantiality which it so pre-eminently deserves.

It may be necessary for the information of some of our readers to premise, that though railways have been for more than a century in use in Great Britain, and are now ex tremely numerous, the one which has been the scene of the present competition is but the third which has been constructed in Great Britain for general use; that is to say, with the view of superseding entirely the employment of ordinary roads, by the public at large, as far as carriages of all descriptions are concerned; and that down to the day of this competition, it was still a question of some doubt whether a railway could be produced possessed of such extensive capabilities.

The first undertaking of the kind was the Surrey Railway, designed by Mr. Jessop; but the only use as yet made of that road has been for the conveyance by horses of heavy goods, at a rate of three or four miles per hour; and in consequence of its pass ing through a country of little traffic, it has rather disappointed the expectations of its projectors.

The second was the Stockton and Darlington Railway, on which steampower was for the first time employed to propel passengers as well as goods, and with a degree of success which began to open the eyes of the public to advantages of which they had not even dreamt in connection with railloway conveyance. It was here proved that by the employment of steamcarriages a speed of from five to eight miles an hour, according to the weight drawn, was readily attainable; and that the expence of this mode of conveyance was one-half, in some in

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stances two-thirds cheaper than any other. Inside passengers were conveyed at the rate of 14d. per mile, outsides, 1d.; and the price of coals, which used at Stockton to be 15s. and 17s. per ton, was all at once reduced to 10s. 2d. From the 29th of September, 1825, when this railway opened, to the 29th of September, 1826, its receipts increased progressively from £700. to £1500. a month; and in the second year it had drawn to it nearly the whole carrying-trade between Stockton, Richmond, Darlington, Yarm, &c. The turnpike-road, too, which may be said to have been thus beaten out of the field, is actually four miles shorter than the railway; for to accommodate Darlington and Yarm, a more circuitous line was taken than would otherwise have been necessary,

As early as 1822, and of course long before these favourable results were known, the Liverpool and Manchester Railway had been projected by William James, Esq., Civil Engineer, and all the necessary surveys for it made by Mr. Vignoles, another able and intelligent member of the same profession; but in consequence of the strong opposition which was threatened by the whole body of canal proprietors throughout the kingdom, and other causes, the prosecution of the design languished till the progress of the Stockton and Darlington Railway towards completion; and the success of some preliminary trials upon it, animated the people of Lancashire with a new zeal in behalf of their own speculation. A deputation of gentlemen was appointed, consisting of Messrs. Ellis, Sanders, and Booth, of Liverpool, and Mr. Kennedy, of Manchester, to proceed to the north to inspect the Stockton and Darlington Railway, and also some collieries in the north of England, where locomotive steam-engines have for several years been employed to transport the coal-waggons to the nearest land or water communication. The report made by this deputation was so satisfactory, that it was immediately determined to prosecute the plan of the Liverpool and Manchester Railway with the greatest vigour: the whole capital required was subscribed within