298 Sir Benjamin Thompson’s 
coldnefs is increafed. Every body knows how very difagreeable 
a very moderate degree of cold is when the air is very damp ; 
and from hence it appears, why the thermometer is not always 
a juft meafure of the apparent or fenfible heat of the atmo- 
fphere. If colds or catarrhs are occafioned by our bodies being 
robbed of our animal heat, the reafon is plain why thofe dif- 
orders prevail moft during the cold autumnal rains, and upon 
the breaking up of the froft in the fpring. It is likewife plain 
from whence it is that fleeping in damp beds, and inhabiting 
damp houfes, is fo very dangerous ; and why the evening air is 
fo pernicious in fummer and in autumn, and why it is not fo 
during the hard frofts of winter. It has puzzled many very 
able philofophers and phyficians to account for the manner in 
which the extraordinary degree or rather quantity of heat is 
generated which an animal body is fuppofed to lofe, when ex- 
pofed to the cold of winter, above what it communicates to 
the furrounding atmofphere in warm fummer weather ; but is 
it not more than probable, that the difference of the quantities 
of heat, a&ually loft or communicated, is infinitely lefs than 
what they have imagined ? Thefe inquiries are certainly very 
interefting ; and they are undoubtedly within the reach of 
well contrived and well conduced experiments. But taking 
my leave for the prefent of this curious fubjefl: of inveftiga- 
tion, I haften to the fequel of my experiments. 
Finding fo great a difference in the conducing powers of 
common air and of the Torricellian vacuum, I was led to 
examine the conducing powers of common air of different 
degrees of denfity. For this experiment I prepared the ther- 
mometer N° 4. by flopping up one of the fmall glafs tubes 
paffing through the ftopple, and opening a paffage into the 
cylinder, and by fitting a valve to the external overture of the 
other. 
