f 134 ] 
healthy perfon, 19 years old, and 
found one meafure of it and one of 
nitrous air to occupy 1.84; which 
convinced me that the air evaporat- 
ing from the fkin of young people 
is not purer than that emitted from 
the {kin of people more advanced 
in years; and that if there fhould 
be any advantage for old people to 
fleep in the fame bed with young 
ones, as fome imagine, it cannot 
likely be owing to their perfpiring 
a better and wholefomer air from 
their {fkin. . It isa very erromeous 
opinion, and even tending to do 
material mifchief, that the air of a 
room, in which a great number of 
young people have been fhut up, 
as in f{chools, is become very whole- 
_ fome for old people to breathe in. 
____Thave feen fchool-mafters fo ftrong- 
dy prejudiced with this notion, that 
