1819.] Scientific Intelligence. 143 
pendulum. Ithas also received the approbation of other eminent 
men in the scientific world. The Society adjudged its gold 
Isis medal, to be presented to Mr. Hardy, for this vention. 
Mr. Einslie’s Ivory Paper.—This paper possesses a surface, 
having many of the valuable properties of ivory, and at the same 
time has the superior advantage of being obtained of a much 
greater size than ivory can possibly furnish, even nearly as large 
as the usual sheets of drawing paper. The Society has voted 
the sum of 30 guineas to Mr. Einslie for this invention. 
Mr. Alexander Bell’s New Chuck for a Lathe.—This instru- 
ment can be screwed into, or upon, the mandrel of a lathe, 
and has three studs projecting from its flat surface, forming 
an equi-lateral triangle, and which are capable of being moved 
equably to, or from, its centre. These studs are provided 
with teeth, and can be made to embrace, or enclose, any hollow, 
or solid, circular body between them, within the extent of its 
limits, and retain it firmly, in order to turn, bore, or operate, in 
any other manner upon it in the lathe. From the greater sim- 
plicity of its construction, it can be made much cheaper than 
similar contrivances for the same purpose. The Society awarded 
its silver medal and the sum of 10 guineas to Mr. Bell for this 
invention. 
ArticLe XII. 
SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 
CONNECTED WITH SCIENCE. 
I. Method of determining the Specific Gravity of the Gases. 
The apparatus necessary for taking the specific gravities of 
gases, by the following method, consists of a delicate balance, 
or rather beam, so constructed that two bulky vessels of 
exactly the same size and weight may be conveniently suspended 
from its extremities. One of these vessels may be a globe, or 
flask, furnished with a stop-cock as usual, and of any convenient 
size. The other must be cylindrical, so as to admit of bemg 
raduated ; say, into 1000 equal parts ; and must be likewise 
urnished with a stop-cock having an extremely minute aperture. 
The two vessels, as before stated, must be exactly of the same 
size and weight, so that, when filled with atmospheric air and 
suspended, the index of the beam shall stand at 0, and these easy 
adjustments are the whole that are required. When used, the 
globe, or flask, is to be filled with the gas, whose specific gravity 
1s to be determined in the usual manner, and the cylindrical 
vessel is then to be so far exhausted as to be rendered lighter 
than the globe, or flask, thus filled. Both vessels being now 
suspended, one at each extremity of the beam, the stop-cock of 
