L 493 3 
XXVI.- Of the Degrees and Quantities of Winds requijite 
to move the - heavier- Kinds -of Wind Machines, In a 
Letter from John Stedman, M. D. Fellow of the Royal 
College of Phyficians- at Edinburgh, to the Reverend 
Samuel Horfley, LL.D. Secretary to the Royal Society . . 
s I R, 
Edinburgh, 
March 27, 1777, 
Read Apr. 24, \r I "'HE irregularity and uncertainty of winds 
in this country have been found a con- 
liderable difcouragement to ere£t wind machines. It 
hath frequently happened, that the proprietors of coal 
and other works, after having reared thefe kinds of en- 
gines, and having found them inefficient for the in- 
tended work, have been obliged to open mines, or to 
erect fire machines. This is chiefly owing to the under-?- 
takers reckoning upon more winds of a efficient power, 
to move thefe machines, than we commonly have in this 
country. . 
Thefe machines are rarely erected with us, unlefs 
where a confiderable moving power is neceflary. This 
is always the cafe where the larger kind of pump-work 
is to be kept in motion, or where water is to be extracted 
from. 
