iq8 Mr, cavekdish’s Account of 
much to explain many of the phenomena attending the mix- 
ture of common and nitrous air. 
The apparatus I ufe is as follows. A (fig. i.) is a cylin- 
drical glafs ve&el, with brafs caps at top and bottom ; to the 
upper cap is fitted a brafs cock B ; the bottom cap is open, but 
is made to fit clofe into the brafs focket Dd, and is fixed in it 
in the fame manner as a bayonet is on a mufquet. The focket 
Dd has a fmall hole E in its. bottom, and is fattened to the 
board of my tub by the bent brafs F fG, in fucli manner that 
b , the top of the cock, is about half an inch under water ; 
confequently if the veflel A is placed in its focket, with any 
quantity of air in it, and the cock is then opened, the air will 
run out by the cock, but will do fo very (lowly, as it can 
efcape no fatter than the water can, enter by the fmall hole E 
to fupply its place. 
Betides this veflel, I have three glafs. bottles like M (fig. 2.) 
each with a flat brafs cap at bottom to make it ttand tteady, 
and a ring at top to fufpend it by, and alfo fome meafures of 
different flzes fuch as B (fig. 3.) ; thele are of glafs with a flat 
brafs cap at bottom and a wooden handle. In ufing them they 
are filled with the air wanted to be meafured, and then fet 
upon the brafs knob C fitted upon the board of my tub below 
the furface of the water, which drives out fome of the air, 
and leaves only the proper quantity. This meafure is eafier 
made, and more expeditious in ufing, than the Abbe Fon- 
tana’s, and, I believe, is. equally accurate ; but if it was not 
it would not fignify, as I determine the exa£f quantity of air 
ufed by weight. 
There are two different methods of proceeding which I have 
ufed ; the firft is to add the refpirable air (lowly to the nitrous ; 
and the other, to add the nitrous air in. the fame manner to the 
refpirable. 
