S70 Mhtory of Mechanical Inventions. 
4. Description fa Ductilimeter for comparing the duciiliiy 
of different Metals. By M. Regniee. 
Tliis instrument, which is represented in Plate Y. Fig. 4., is 
intended for ascertaining and comparing the ductility of differ- 
ent fusible metals, as lead^ tl% &c. It consists of a hammer, 
AB, made of iron, and moving round a horizontal axle B, a 
w^ooden 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 con- 
centric circles engraven on the iron plate. The hammer AB is 
then raised to the 50th degree of the are MN, and is allow- 
ed 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 mea- 
sure of the comparative ductilities, the following are some of the 
results obtained by M. Regnier : 
Blows of the hammer. 
Old lead remelted TO times, - - » 10 
New lead of Sir W. Blackett, - - - 11 
Do. of Caldebek, • - - 12 
Lead containing ^ tenth part of zinc, - - 14i 
Tin of Cornwall, - - .40 
See the Annates des Mines ^ tom. vii. p. 13. 
5. On the Fahrication cf Artificial Pastes in Imitation of Pre- 
cious Stones. By M. Doualt Wieland. 
A prize having been offered by the Society for the Encou- 
ragement of the Arts in France for the best memoir on the sub- 
ject, it w^as 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. 
The following three mixtures give a very .fine .strass : 
Rock Crystal, 
0.318 
0.31 TO 
0.300 
Minium, 
0.490 
0.4855 
0.565 
Potash, pure, 
0.170 
0.1 7T0 
0.105 
Borax, « • 
0.021 
0.0200 
0.030 
Arsenic, oxide of, 
0.001 
0.0005 
1.000 
1.0000 
1.000 
