proposed, because we know that the ice-boat upon the great ca nal before mentioned, with the power of a few horses, breaks the very solid ice of the canal, where it forms a firm compact sheet from bank to bank.

I need not enter upon all the various advantages which will arise from the establishment of this steam-boat: they are obvious to every one who is acquainted with this district of country. At present I cannot give an exact account of the distance which will be saved in travelling by this route from Perth to Glasgow. The road, however, will be shortened at least from twelve to fifteen miles, which is of great importance to travellers.

According to my view, the steam-boat will ply summer and winter, from morning light till dusk; the small boats and crew being always ready for crossing the river during the night, in case of emergency, or during the repairs of the engine in the day.

I estimate the weekly expence of the steam-boat to be as follows:

3. Mr HARFORD's Improvements on Puddling Furnaces. In that department of the manufacture of iron called puddling, cast-iron bottoms or floors have been generally employed, but as these bottoms decay rapidly, and as it has been found that the iron slag, scoria or sand, which are employed to defend these bottoms from injury, impart impurities to the iron, Mr Harford has adopted the following mode of rendering them durable, which he has secured by patent. He spreads over the cast-iron bottoms a quantity of charcoal, reduced to powder, which being a bad conductor of heat protects the cast-iron floors better than any other substance, from the intense heat which is required in these furnaces. This very simple contrivance is said to produce iron of a very superior quality.

4. Description of a Ductilimeter for comparing the ductility of different Metals. By M. REGNier.

This instrument, which is represented in Plate V. Fig. 4., is intended for ascertaining and comparing the ductility of differ ent fusible metals, as lead, tin, &c. It consists of a hammer, AB, made of iron, and moving round a horizontal axle B, a wooden quadrant MN fixed in the wooden frame EF, and a plate of iron C, on which is fixed the ball of lead or tin. The lead or tin is fused into regular balls, about 10 millimetres in diameter, and each ball is laid upon the centre of several concentric circles engraven on the iron plate. The hammer AB is then raised to the 50th degree of the arc MN, and is allowed to descend upon the balls. By successive blows, the balls are enlarged to circular discs, 30 millimetres in diameter, and the number of blows necessary for this purpose will give a measure of the comparative ductilities, the following are some of the results obtained by M. Regnier :

See the Annales des Mines, tom. vii. p. 13.

Blows of the hammer.

10

11

12

14

40

5. On the Fabrication of Artificial Pastes in Imitation of Precious Stones. By M. DOUALT WIELAND.

A prize having been offered by the Society for the Encouragement of the Arts in France for the best memoir on the subject, it was decreed to M. D. Wieland.

The base of all these imitations is Strass, or White Crystal. The materials employed are melted in Hessian crucibles, and a porcelain furnace, or, what is preferable, a potter's furnace is afterwards used. The more tranquil and prolonged that the fusion is, the more hardness and beauty does the strass acquire. Strass.-The following three mixtures give a very fine strass:

Topaz-The imitation of topaz is difficult. It passes from the white of strass to sulphur-yellow, violet and red purple, according to circumstances which are not determined. The following are two of M. Wieland's recipes:

These mixtures sometimes yield an opaque mass, translucent at the edges, and of a red colour in thin plates. By mixing it with eight times its weight of strass, and keeping the mixture in fusion for thirty hours in a potter's furnace, the result is a fine yellowish crystal. This crystal re-melted by the blowpipe, produces the finest imitation of eastern Ruby.

Ruby.-A ruby less beautiful, and of a different tint, may be made thus:

Emerald.-This paste is very easily made; and that which approaches the nearest to the mineral is the following:

Peridot.-By augmenting the proportion of oxide of chrome and oxide of copper in the first composition of emerald, and adding oxide of iron, we may vary the green shades, and imitate the peridot and deep coloured emerald.

This mixture must be put into a Hessian crucible, carefully luted, and remain thirty hours in the fire. If the process is well conducted, the result will be a very hard glass, without bubbles.

Amethyst. Very deep amethyst may be obtained with

Syrian Garnet.-This paste is used for small jewels, and is

In the fabrication of the pastes, many precautions are neces sary, which can be learned only by experience. The materials should in general be carefully pulverised. The mixtures should be properly sifted, and the same sieve should not be used for different compositions. In order to obtain the glass well melted, and homogeneous, and without striæ and bubbles, materials of great purity must be employed;-they must be mixed in a state of extreme tenuity;-the best crucibles must be used;-the fire

must, be graduated, and kept equal to the maximum temperature, and the mass must be left in the fire from 24 to 30 hours, and allowed to cool very slowly.-See Bulletin de la Societé d'Encouragement, tom.'xviii. p. 311.

6. Description of a New Blowing-Machine.

This blowing-machine, which is used in the Hartz, is represented in Plate V. Fig. 5. It consists of a chain of floats moving round a wheel A. These float-boards are impelled by the weight of the current of water MN; and it is manifest, that, for a given velocity of the machine, the quantity of water admitted upon the floats may be such, that the space between two consecutive floats shall not be filled with water. The rest of the space will therefore be filled with air, which will be conveyed into the reservoir R, and will escape at S, or may be conducted wherever we please. The theory of this machine has been investigated by M. Clapeyron. The great simplicity of this blowing-machine may render it very useful, under particular circumstances; but it is obvious that the friction must be considerable.See the Annales des Mines, tom. vii. P. 3.

7. Account of Improvements made on Steam-Packets, and other Vessels. By DAVID GORDON, Esq.

Mr Gordon, to whom the public is indebted for the portable gas-lamp, and other inventions, has taken out a patent for different improvements on Steam-Packets.

Fig. 6. of Plate V. represents an horizontal plan of the deck of a steam-boat or steam-packet, adapted to sea or river navigation, constructed according to Mr Gordon's improvements; and Fig. 7. a longitudinal section of the same. A represents the paddle-wheel, which may be constructed in the manner of ordinary steam-boats; but it is inclosed in a case in such a way that the sides or edges of the paddles have just liberty to move freely between the sides of the case; the wheel is inclosed by the case in front (or towards the bow of the vessel), leaving only an aperture at a for the water to arrive at the paddles of the wheel; and this aperture should be entirely below the VOL. VII. NO. 14. oct. 1822. Bb