Memoir on Sulphuric Ether. 463 
of the experiment it is to be ascribed to the 
depth of the surface of fluid in the tube, and 
the partly saturated air. 
Though convinced the above results were 
very good approximations, I was desirous to 
have a confirmation of it by some more di- 
rect method.—I took a bottle of the capacity 
of 2600 grains of water, and graduated ac- 
cordingly ; this being filled up to 1100 grains 
with dry mercury, was inverted in the mercu- 
rial trough with 1500 common air. Through 
this mercury were passed 1, 2, 3 or more 
grains of ether, which expanded the air, 
and from the quantity of expansion, com- 
pared with the weight of ether let up, the 
specific gravity of the vapour was inferred. 
This method did not give uniform results 
owing to a considerable portion of such mi- 
nute quantities of ether being entangled by 
the mercury inits passage. 'To remedy this, 
I took a small tube, + of an inch in diameter 
internally, and 2 inches long, which was 
sealed at one end, and then graduated into 
water grains, which was such as to allow 
nearly 4 of aninch for one grain. This was 
filled with mercury, except for 1, 2 or more 
grain measures, which were afterwards filled 
with ether, and the finger being applied, the 
tube was plunged into the mercury and passed 
