146 FERGUSON'S LECTURES. 



of ale gallons. Also, the troy ounces divided by 12, 

 , will reduce the weight to troy pounds ; and the avoir- 

 dupoise ounces divided by 16, will reduce the weight to 

 avoirdupoise pounds. 



And here I must repeat it again, that the weight or 

 pressure of the water acting against the power that 

 works the engine., must always be estimated according 

 to the perpendicular height to which it is to be raised, 

 without any regard to the length of the conduct-pipe, 

 when it has an oblique position ; and as if the diame- 

 ter of that pipe were just equal to the diameter of that 

 part of the pump in which the piston works. Thus, by 

 the following tables, the pressure of the water, against 

 an engine whose pump is of a 4i inch bore, and the 

 perpendicular height of the water in the conduct-pipe 

 is 80 feet, will be equal to 8057.5 troy ounces, and to 

 8848.2 avoirdupoise ounces ; which makes 671.4 troy 

 pounds, and 553 avoirdupoise. 



EXAMPLE. Required the number of cubic inches, and 

 the weight of the water, in an upright pipe 278 feet high, 

 and la inch diameter? 



Cubic Troy Avoird. 

 Feet inches oz. oz. 



200 4241 .12238.2 2457.8 



701484.4- 783.3 860.2 



8 169.6 89.5 98.3 



Ans. 2785895.13111.03416.3 



Here the nearest single decimal figure only is taken 

 into the account : and the whole being reduced by 

 division, amounts to 25i wine gallons in measure ; to 

 259j pounds troy ; and to 213i pounds avoirdupoise. 



For any bore whose diameter exceeds 6j inches, 

 multiply the numbers on the following page against 

 any height (belonging to 1 inch diameter) by the square 



