[ III ] 
Counter- weight, for 30 turns without water, 1 oz. in 
the fcale. 
N. B. The area of the head was 105,8 fquare inches. 
Weight of the empty fcale and pulley, 10 oz. 
Circumference of the cylinder, 9 inches. 
Circumference of the water-wheel, 75 ditto. 
Reduction of the above Sett of Experiments . 
The circumference of the wheel, 77 inches, mul- 
tiplied by 86 turns, gives 6470 inches for the velo- 
city of the water in a minute 5 do of which will be 
the velocity in a fecond, equal to 107,7 inches, or 
8,96 -feet, which is due to a head of 1 7 inches * ; 
and this we call the virtual or effective head. 
The area of the head being 105,8 inches, this 
multiplied by the weight of water of the inch cubic, 
equal to the decimal ,779 of the ounce avoirdupoife, 
gives 6 1, a 6 ounces for the weight of as much water, 
as is contained in the head, upon 1 inch in depth, 
7V of which is 3,83 pounds 5 this multiplied by the 
depth 2 i inches, gives 80,43 lb. for the value of 12 
flrokes ; and by proportion, 394 (the number made 
in a minute) will give '264,7 lb. the weight of wa- 
ter expended in a minute. 
Now as 264,7 lb. of water may be conlidered as 
having defcended through a fpace of 1 5 inches in a 
minute, the product of thefe two numbers 3970 will 
exprefs the power of the water to produce mechanical 
effects j which were as follows. 
* This is determined upon the common maxim of hydroftatics, 
that the velocity of fpouting waters is equal to the velocity that 
an heavy body would acquire in falling from the height of the 
refervoir; and is proved by the rifing of jets to the height of their 
refervoirs nearly. 
The 
