80 
“ The ether I used boiled in the open air at 102°. 1 filled 
a barometer tube with mercury moistened by agitation in 
ether ; after a few minutes a portion of the ether rose to the 
top of the mercurial column, and the height of the column 
became stationary. When the whole had acquired the 
temperature of the room (62°) the mercury stood at 17*00 
inches, the barometer being at the same time 29*75 inches. 
Hence the force of the vapour from ether at 62° is equal to 
12-74 of aqueous vapour at 172° temperature, which are 40° 
from the respective boiling points of the liquids.” 
This is generally known as Dalton’s law of tensions, since 
shown by Hegnault not to be rigorously true. 
No. 18 is a wet and dry bulb mercurial thermometer 
made by H. H. Watson, of Bolton. 
III. Apparatus for Measuring Gases, and for determining 
the Solubility of Gases in Water. 
No. 19 is an apparatus with a graduated tube, probably 
used by Dalton for the determination of the laws regulating 
“ the absorption of gases by water and other liquids,” read 
October 21st, 1803*. No. 20 is a graduated glass tube 
attached to a bottle of indiarubber, also probably used in 
his researches on the absorption of gases by water. No. 21, 
No. 22, are divided endiometer tubes, employed by Dalton 
for measuring the volumes of gases. No. 23 is a spark eudi- 
ometer ; Nos, 24, 25, 26 are glass tubes, pipettes, and 
funnels graduated by Dr. Dalton and used by him for 
measuring gases ; No. 27 is a graduated glass bell-jar, used 
for measuring gases ; No. 28 is a phial, with graduated tube 
attached by cement, for collecting and measuring gases; 
Nos. 29, 30 are stoppered phials with the bottoms cut off, 
used as gas jars for collecting and measuring gases; No. 31 
is a thousand grains specific gravity bottle, with its counter- 
poise of lead stamped “175” and paper labelled “bottle 
# “Manchester Memoirs,” 2nd Series. Vol. 1. 
