GRAVITY OF VAPOUR. 163 
A small glass bulb was prepared and its capa- 
city determined by weighing it when filled with 
mercury. It was then filled with the liquid un- 
der examination, care being taken not to put 
in more than would be vapourized. This being 
done it was again carefully weighed and passed 
(the tube standing in a basin of mercury) 
up into the vacuum above; the basin and the 
tube containing the mercury were now attached 
to a wooden frame. A scale graduated to inches 
and tenths was attached on one side of the tube, 
and a thermometer on the other side, and the 
apparatus was now removed into the room be- 
fore described, in which the temperature was 
at first 200° and rose gradually for three days 
until it became 250°. To secure a uniform 
temperature in the instrument it was suspended 
in the middle of the room out of the reach of 
all currents of air. 
VAPOUR OF WATER. 
The forty two inch tube was used: the capa- 
city of which is 4.64 cubic inches. 
3.46 capacity of the ball. 
—— 
8.10 TOTAL. 
