r 255 I 
lumn of water, having its bafe equal to the furface that: 
is oppofed, and its height equal to the altitude of the co- 
lumn of water fuftained by the wind in the wind-gage. 
Hence the force of the wind upon any body where the: 
furface oppofed to it is known, may be eafily found ; and 
a ready comparifon may be made betwixt the Hrength' 
of one gale of wind and that of another, by knowing - 
the heights of the columns of water,' which the different 
winds were capable of fuflaining.^ The heights of ther 
columns in each leg will be equal, provided the legs are ' 
of equal bores ; but unequal, if their bores are unequal. 
For fuppofe the legs equal, and the column of water the 
wind fuftains to be three ’inches, the Water in the leg,v 
w^hich the wind blow^s into, will be depreffed one inch, 
and a half below o, and raifed juft as much above it irii 
the other leg. But if the bore of the leg which the 
wind blows into, be double that of the other, the w^atef 
in that leg will be depreffed only one 'inch, w^hilft it is 
raifed twice as much, or two inches, in the other; and- 
vice verjd^ if the fame wind blow into the fmaller leg,' 
it will deprefs the water in it two inches, whilft it raifes 
it only one inch in the other. The force of the wind 
may be iikewife meafured with this inftrument, by fill- 
ing it until the water runs out at the hole g. For if we 
then hold it up to the wind as before, a quantity of av a- 
ter will be blown out ; and, if both legs of the inftru- 
ment are of the fame bore, the height of the column 
fuftained, will be equal to double Ihe column of water 
in either leg, or the fum of what is wanting in both legL' 
BtiX 
