* 
E... 47827] 
There are two other great fources 
of errors that may be committed in 
the examination of any refpirable 
air by the nitrous teft, which Abbé 
Fontana has allo pointed out and 
corrected, 
The firft of thefe two refides in 
the act of mixing the two airs. If 
the nitrous air is let up into the large 
tube, in which was already the air 
to be examined, and the tube put 
by for a while without fhaking it, 
“tO give time to. the two airs to incor- 
porate with one another; or if the 
two airs are firft put in a feparate 
veffel. before they are let up into 
the darge- tube; there will {carcely 
ever be two experiments correfpond- 
ing with one another; the differ- 
ence will be fo great, and the refult 
fo uncertain, that it may amount 
- in one experiment to anserror of © 
‘fifty 
oy 
, 
