i66 Anal^fts of the Air. 
being found as above 21635 fquare inches 
only part of an inch depth, will be 
evaporated off their inward furface in that 
time, which is but 3-9 part of the depth of 
what is perfpired off the furface of a man's 
body in that time. 
If then life can by this means be fup- 
ported for 5 minutes with 4 T^iaphragms 
and a gallon of air, then doubtlefs, with 
double that quantity of air and 8 T>iaphragms 
we might well exped to live at leaft 10 
minutes. It was a confiderable difadvantage 
that I was obliged to make ufe of bladders, 
which had been often wetted and dried, fo 
that the unfavory fumes from them muft 
needs have contributed much to the unfitting 
the included air for refpiration : Yet there 
is a neceflity for making ufe of either blad- 
der or leather in thefe cafes 5 for we can- 
not breath to and fro the air of a vefici, 
whofe fides will not dilate and contrad in 
conformity with the expirations and in- 
fpirations, unlefs the veflel be very large, and 
too big to be conveniently portable. 
Having flopped up the wide fucking orifice 
of a large pair of kitchen bellows, they be- 
ing firft dilated, I could breathe to and fro 
at 
