52 Dr. Darwin’s frigorijic Experiments , &c. 
Cental cold, or by any other caufe not yet underftood (as the 
combination of dephlogiftic and inflammable gafes), the air 
next in vicinity fuddenly expands itfelf to occupy the vacuity ; 
and by its expanlion produces cold and devaporates, and then 
becomes comprelhble into lefs fpace than it occupied before it 
parted with its vapour. This then gives occafion to the next 
circum-ambient portion of air to go through the fame procefs, 
that is, to expand, attract the heat from its vapours, devapo- 
rate, and then become compreffible into lefs fpace ; and thus, 
from a fmall and partial contraction or diminution of air,- it 
feems poffible to devaporate a great province. 
2. The vapour of a great province of air being thus condenfed, 
would leave a great vacuity in that part of the atmofphere, 
which would be fupplied by winds rufhing in on all fides. 
Suppofe this to happen to the north of our climate, a fouth-weft 
wind would be produced here, which is otherwife very difficult 
to underftand : and if it ffiould ever be in the power of human 
ingenuity to govern the courfe of the winds, which probably 
depends on fome very fmall caufes ; by always keeping the under 
currents of air from the S.W. and the upper currents from the 
N.E. I fuppofe the produce and comfort of this part of the 
world would be doubled at lead: to its inhabitants, and the dif- 
covery would thence be of greater utility than any that has 
yet occurred in the annals of mankind. 
November 22, 178 7. 
