138 Remarks on Priesiley’s Analysis 
This philosopher thinks he has discovered, that 
atmospherical air contains much more’ pure air, 
than has hitherto been found. He makes the pro- 
portion of it amount to 46.6 parts in a hundred,: 
instead of 27 parts. He has found, that equal mea- 
sures of nitrous and atmospherical air mixed toge- 
ther (though, at first, they occupy a space of 1.01 
measures) will, in the course of a month, occupy 
only 0.6 of a measure.—That this fact does not 
warrant the conclusion he draws from it, will appear 
by what the same chemist relates in the 1st vol. of 
his Experiments, p. 361. “ Having mixed,” says 
he, a “ quantity of air, which I knew to be thorough- 
ly phlogisticated by the putrefaction of fishes, with 
an equal quantity of nitrous air; I transferred the 
mixture into my graduated tube, when, instead of 
occupying two whole measures (as I had expected) 
they only occupied 1.95 measures. I poured the 
air back again into a wide jar; and, transferring it 
once more into a graduated tube, found it to be on- 
ly 1.8 measures; and pouring it about ten times 
backwards and forwards, without any unnecessary 
agitation, it was reduced to 1.6 measures. Having 
stood in water all night, 1 measured it again the 
next morning, when J found zt to be 1.5; and by 
measuring three times more, it was,reduced to 1.4.” 
To whatever, therefore, the farther diminution of 
a mixture of these two gases, by standing over water 
for a long time, may be owing, it is certain that it is 
