To enable the few undercut parts, that occur in artificial palates, to be carved by the dentifactor, Mr. Tomes now makes the slide that carries the disks not with one flat surface, but to have two inclined and parallel planes, that serve as the foundations for the circular disks, and which latter are connected by one long tangent screw that moves the two upon their axes, similarly and equably; so as by the angular change of the disks which carry the work and model, to place the few undercut parts successively at the lowest sides of the inclines, or at the bottoms of the hills, when such undercut parts (unless they exceed in inclination 20 degrees, and which never occurs in this branch of art), slope the reverse way, bo as to be conveniently accessible to the revolving cutter.

The dentifactor was constructed in the author's manufactory, and he therefore feels increased pleasure in announcing the complete efficacy of Mr. Tomes's project, which was favourably noticed in the Minutes of Conversation of the Institute of Civil Engineers, page 250; in the Medical Gazette, p. 161,and numerous other publications, and for which invention Mr. Tomes received the Gold his Medal of the Society of Arte, - all in 1845.

Note M. Page 121. - To precede the bat two lines.

Slag and buck-born admit of being partially straightened, whoa in thin pieces or scales, to adopt them to the forma of the handles of pan and pocket knives. To effect this, a dosen pieces of the stag or buck-born, when reduced nearly as thin as required, are thrown into a vessel of water almost boiling, and on removal one at a time, are flattened or untwisted, by grasping their ends between pliers, and at raining them into form, after which they are allowed to cool in the air, or are some-timea dipped in cold water. The under sides of the scales are then filed or reaped upon a strip of iron held in the fatting vice, repreeented in fig. 864, page 864.

Stag-horn and buck-horn are considered to become more brittle from the immer-eion, which is therefore made as short as possible. Stag-horn, buck-horn, ivory and pearl-shell, especially the first, are somewhat liable to cause rust on the steel works of knives, not so however tortoiaeshell, or buffalo and similar horn.

Note N, Page 155 - To follow the first paragraph. (Isinglass glue.)

" If it be wished to dissolve good isinglass in spirits of wine, it should first bo allowed to soak for some time in cold water, when swelled it is to be put into the spirit, and the bottle containing it being set in a pan of cold water may be brought to the boiling point, when the isinglass will melt into a uniform jelly, without lumps or strings, which it is apt to have if not swelled in cold water previously to being put in spirits; a small addition of any essential oil diminishes its tendency to become mouldy."

"If gelatine which has been swelled in cold water, be immersed in linseed oil and heated, it dissolves and forms a glue of remarkable tenacity, which when once dry perfectly resists damp, and two pieces of wood joined by it will separate anywhere else rather than at the joint Ordinary glue may be thus dissolved and sometimes a small quantity of red lead in powder is added." Sir J. Robison.

Note 0, Page 160 - 161. (Prosser's patent process for works made of dry clay.)

The first line of the article on clay, which ran as follows: "This material is only worked in the soft and plastic state," is unintentionally erroneous, as the author since learns that Mr. Mencke obtained in 1828 a patent for manufacturing bricks and tiles from dry pulverized clay, containing a quantity of moisture not exceeding one per cent., the clay was pressed forcibly into moulds and immediately baked, without the necessity for its being dried, and from the dense condition of the compressed mass, without the risk of cracking in the fire.

Mr. Rowland Prosser's patent, 1840, is for a similar but superior employment of dry clay, sometimes mixed with colouring matters, for making buttons, rings, knobs, the tessera) for pavement, and other things. The dry powder is put into a deep mould, that holds just the right quantity, and terminates at foot in the bottom die, the top die is attached to the fly-press, descends within the tube, and moulds the object, making the four holes in the button at the same moment The pieces are released from the mould by a piston or rammer pressed upwards as usual by a treadle or otherwise. This patent is successfully worked by Messrs. Minter of Stoke-upon-Trent

Note P, page 191, to precede Section IV.

{Clay's patent process for manufacturing wrought iron.)

The author transcribes from the Minutes of Conversation of the Institution of Civil Engineers for 1843, page 82, a part of the account of this process.

"By the ordinary system of iron-making, the ores are reduced into the state of carburet of iron, and then, by refining and puddling, the metal is de-carburetted, thus making it into malleable iron by a number of processes which are recapitulated: - "

" 1st. Calcining the ore.

"2nd. Smelting in a furnace, by the aid of blast, either cold or heated, with raw coal, or coke, for fuel, and limestone as a flux.

" 3rd. Refining the ' pig' into ' plate' iron.

"4th. Puddling, shingling, and rolling, to produce 'merchant' or No. 2. bars.

" 6th. A repetition of the same process to make ' best' or No 3. bars."

"Seeking to diminish the number of manipulations by the new process a mixture of dry Ulverstone, or other rich ore (Haematite,) is ground with about four-tenths of its weight of small coal, so as to pass through a screen of one-eighth of an inch mesh. This mixture is placed in a hopper, fixed over a preparatory bed, or oven, attached to a puddling furnace of the ordinary form. While one charge is being worked and balled, another gradually falls from the hopper, through the crown upon the preparatory bed, and becomes thoroughly and uniformly heated; the carburetted hydrogen and carbon of the coal, combining with the oxygen of the ore, advances the decomposition of the mineral, while by the combustion of these gases, the puddling furnace is prevented from being injuriously cooled. One charge being withdrawn another is brought forward, and in about an hour and a half the iron is balled, and ready for shingling and rolling."