of Winds requijite to move heavy Wind Machines. 49 5 
and of colds in winter are very confiderable. The periods 
of the year here meant will generally be found to fall 
near the Equinoxes. 
The only method of bringing the matter to a proper 
eftimate is, by comparing the quantities of winds fuffi- 
cient for moving thefe machines, with thofe of winds be- 
low that degree, and calms. This computation can only 
be drawn from journals in which the degrees of winds 
are noted. In the meteorological regifter of the Medical 
E flays of the Edinburgh Society, there is a column of 
winds, and four degrees are noted. This divifion is fuf- 
ficient for the purpofes for which that regifter was in- 
tended ; but, when we confider the wind as a power 
adting upon machines, that number of degrees will be 
found too fmall. , 
Thus, from the fecond in that regifter to a hurricane, 
there is but one intermediate degree. As the fecond de- 
gree, which is very moderate, is infuffxcient for moving 
thefe machines ; the third is more than juft enough for 
that purpofe. A degree, therefore, which is a mean be- 
twixt thefe two, will be found to be the loweft that is 
fufticient for. moving machines of the heavier kinds, par- 
ticularly fuch as are ufed for pumping water out of 
coal-pit s» , 
Thefe- 
