[ s 27 ] 
that it was fenfibly diminifhed in weight by the 
operation. 
Air thus diminished by the fumes of burning char- 
coal not only extinguifhes flame, but is in the higheft 
degree noxious to animals ; it makes no effervefcence 
with nitrous air, and is incapable of being diminifhed 
any farther by the fumes of more charcoal, by a 
mixture of iron filings and brimftone, or by any other 
caufe of the diminution of air that I am acquainted 
with. 
This obfervation, which refpedls all other kinds 
of diminifhed air, proves that Dr. Hales was mif- 
taken in his notion of the abforption of air in thofe 
circumftances in which he obferved it. For he fup- 
pofed that the remainder was, in all cafes, of the 
fame nature with that which had been abforbed, and 
that the operation of the fame caufe would not have 
failed to produce a farther diminution ; whereas all my 
obfervations not only (hew that air, which has once 
been fully diminifhed by any caufe whatever, is not only 
incapable of any farther diminution, either from the 
fame or from any other caufe, but that it has likewife 
acquired new properties, moll remarkably different 
from thofe which it had before, and that they are, 
in a great meafure, the fame in all the cafes. Thefe 
circumftances give reafon to fufpedt, that the caufe 
of diminution is, in reality, the fame in all the cafes. 
What this caufe is, may, perhaps, appear in the 
next courfe of obfervations, 
G g 2 
VIII. 
