494 Br. stedman on the Degrees and Quantities 
from deep pits. Having enquired of many people con- 
cerned in fuch works, what may be the- proportion of 
time in which wind machines may be kept in motion, to 
that in which they cannot move from a defeCt of wind, 
I found thefe people differing widely in their conjectures. 
Having, however, met with one gentleman of ob- 
fervation and accuracy, who had eredted a wind ma- 
chine for draining his coal ; he told me that, by the belt 
computation he had been able to make, he never could 
depend upon more than fifty-three or fifty-four hours of 
wind fufficient for moving that machine, in a week, 
taking the year round. This is below what is commonly 
believed to be the proportion ; but, fo far as this can be 
rated by an eftimate in the following manner, it will be 
found to be much about what may be depended upon 
for the heavieft kinds of machines ; flill making allow- 
ance for the differences of expofures, and for the ftrength 
and frequency of winds in one part of the country more 
than in another. We may here take notice of a circurn- 
ftance favourable to the draining of coal-pits; that is, 
that the periods of the year in which the greateft quan- 
tities of rain fall, are like wife obferved to abound with 
winds of the higher degrees. This feldom fails to hold 
in hilly countries, and particularly iji thofe of high lati- 
tudes ; that is, where the differences of heats in fummer 
and 
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