Note D, page 284.

"Experiments on the Tenacity of Wrought Iron," by Mr. James Nasmyth, C. E. - Communicated to the Meeting of the British Association, Manchester, 1842.

Mr. Nasmyth commences by entirely objecting to a part of the opinion recently advanced by the French Commission, appointed to inquire into the circumstances of the recent lamentable accident on the Versailles railway; namely, that the axles of railway carriages, although they may be originally good, become gradually deteriorated from electrical or magnetical causes, owing to their revolving In contact with the rails. Mr. Nasmyth, on the contrary, ascribes the mischief principally to the workshop, and considers that the very boat iron may be greatly deteriorated by the continuance of the hammering or swaging until the iron is cold, which, although it adds to the finish and smoothness of the forgings, at the same time detracts, and sometimes enormously so, from their "shock-resisting quality."

Mr. Nasmyth's experiments were made on parts of the same bar of the very beat iron, 1 3/4 inch square, laid obliquely across the anvil, with the end overhanging the same 2 1/2 to 3 inches; the blows of a heavy sledge hammer were directed upon the bar, and immediately over the edge of the anvil

Exp. 1. The bar, in the state in which it 1. ft the manufacturer's hands, and at the temperature of 60°, broke with nine heavy blows, " the fracture exhibiting that clear crystalline texture due to a good quality of iron at that temperature."

Exp. 2. A piece of the same bar, heated red hot and hammered until cold, broke at 60°, with one slight blow, "the fracture exhibiting a most beautiful dote crystalline grain, more like the fracture of steel than iron."

Exp. 3. The latter bar (exp. 2) heated to a dull red, and allowed to cool at its leisure, refused to break, it doubled upon itself, the outer part of the bend became three-fourths of an inch thinner from the extent to which it had been stretched, the inner part became thickened in the same degree from the compression; and after receiving 105 heavy blows, and being doubled or folded down flat, no evidence of fracture was visible.

Exp. 4. A portion of the original bar (1) warmed to 100°, after receiving about fifty blows over the edge of the anvil, curled into the form of a crook, and split open on the outer edge, the fracture being entirely fibrous like wood, of a fine lead gray colour, and totally free from the appearance of any sparkling crystals;" showing remarkable changes from experiment 1, simply by the addition of 40 degrees of temperature.

Mr. Nasmyth thence argues, that temperature greatly influences both the tenacity and the appearance of the fracture in iron; and that the best practice undoubtedly is, to hammer the work until cold, and then to anneal it; " the curative process," being most simple and of insignificant cost See Civil Eng. and Arch. Journal, page 285.

Note E, page 234.

A Machine for Forging Iron and Steel, has been lately invented by a gentleman at Bolton, named Rider. This machine, which was exhibited in action at the Meeting of the British Association at Manchester, is quite portable, occupying a space of 3 feet by 4 feet It may be worked by steam or water power, so as to make about 650 blows per minute.

It contains five or six sets of anvils and swages. The anvils are arranged in a row in the frame at the usual height from the ground, and every swage is fixed to the lower end of a vertical bar, moving between proper guides, so as to be capable of rising and falling through a small space above its anvil A horizontal axis passes across the upper ends of these swage-bars, and has an eccentric for every swage, so that the uniform rotation of this axis causes every one of the swages to rise and fall periodically in order. The workman has merely to heat the bar in the fire, and hold it under the vibrating swage, turning it or otherwise changing its position according to the form he wishes to produce.

It is stated that the machine will perform the labour of three men and their assistants or strikers, and will complete its work in a very superior manner and with great rapidity. Thus a piece of round iron 1 3/4 inch in diameter, was reduced to a square of § inch, 2 feet 5 inches long at one heat.

This swage machine promises to be of particular use in forging such works as cotton spindles and others required in great numbers, as the diameters and lengths of their respective parts, can be determined with the same accuracy as that of objects moulded in sand and cast in the ordinary way; and the forgings require but little adjustment beyond centering, to adapt them to the turning lathe.

Note F. - To follow the Foot Note, page 372.

The Six-foot Speculum. In casting this remarkable work, the Earl of Rosse, (formerly Lord Oxmantown,) used a porous metallic mould with a ring of sand, as before described. The mould was composed of slips of hoop-iron, four inches wide, one-eighth of an inch thick, wedged up tight in a frame, and turned coarsely to the curve on the bed of the grinding-machine, with a rude curvilinear slide-rest

The diameter of the Speculum was six feet and a fraction, thickness in the center five inches, at the edge five and a half inches. Three tons weight of metal, which had been previously run into ingots, was poured from three cast-iron pots into the mould in four seconds of time; the mould was shortly after dragged into the heated annealing oven, and every aperture having been stopped off most carefully the annealing was extended over above two months, and was quite successful.

The Telescope will be erected in a lofty stone tower, with a stage at the top; the speculum will be supported in its tube upon a system of levers, to resolve its bearing to three points only, (as described in the Trans. Royal Soc. 1840, p. 524,) and at the distance of 54 feet, or its focal length, the plane mirror at 45°, and the lateral eye-piece, will be attached to the tube, as in Newton's arrangement. The instrument will be situated in the plane of the meridian with an equatorial movement by clock-work for half an hour on either side, to extend observations for one hour.

The construction of the Reflecting Telescope has been long a favourite pursuit with amateurs, but this instrument is an enormous extension upon any hitherto attempted. The Earl of Rosse does not consider that he has arrived at the mechanical limit of size, but that no further optical advantage is to be anticipated from a larger instrument, owing to atmospherical interferences. This arduous undertaking is expected to be completed in the course of 1843.

Since the above lines were written, the Earl of Rosse has completed his gigantic undertaking in a most satisfactory manner, no alteration from the original intentions having appeared necessary. The observations made with the new telescope, have been found to realise every expectation that had been formed of its powerful and surprising definition.

Note G. - To follow the second paragraph, page 440.

A very convenient 'portable torch, which is much used by the gas-fitters and pewterers, consists of three or four dozen rushes such as are used for rush-lights; they are expressly prepared by the tallow-chandlers with only a slight coating of tallow, and are retained in a paper sheath. This torch may be carried to the work, and used in situations where an ordinary oil lamp could not be applied; the rushes last a considerable time. This description was accidentally omitted in the body of the work, and refers to page 449 as well as to 440.