J. P. Cooke, Jr , on Lecture Experiments, 197 
tube is full. The excess of mercury is now drawn out of the 
open tube by the tap and this tube having been removed the in- 
strument is left as represented in fig. 9. The eudiometer is now 
ready for receiving the mixed gases, which are passed up into it 
from a simple decomposing cell, as shown in the figure, the ex- 
S00 
eudiome 
fasily be told, because the mercury 
column will then remain at a constant i 
height, mercury must be poured into the open tube or with- 
wn from it by the nipper tap until the level is the same in 
both limbs of the apparatus. It remains now only to note the 
Volume of the confined gas and to explode it by passing an elec- 
tric Spark through the platinum wire already noticed, first, how- 
*ver, tightly closing the end of the open tube with its rubber 
Stopper, When the stopper is removed and the mercury col- 
amns again brought to the same level it will be found that the. 
Ume of the confined gas has been reduced one- 
, even at the boiling point of amylic alcohol, 132° C., does 
~* €xactly obey Mariotte’s law, and is somewhat con- 
