SECTION IX. 



OF THE APPLICATION OF STEAM ENGINES TO DIFFERENT PURPOSES. 



569. THE great variety of objects to which steam power is or may be applied, 

 renders it necessary to confine our attention to the most prominent ones for 

 illustration. These are to raising water ; to impelling machinery for mining, 

 manufacturing, and agricultural purposes; and to land carriage: the application 

 to navigation however is so distinct and important as to require a separate 

 treatment ; and it is therefore reserved for the next section. 



OF RAISING WATER. 



570. Water is generally raised by means of pumps of the lifting or forcing 

 species. The stroke of a pump should not exceed about eight feet, otherwise the 

 air disengaged from the water, the escape by the bucket or piston, and the defect 

 of pressure on the fluid which is rising after the piston, becomes greater than the 

 escape by the valves. The velocity of the piston should not exceed 98 times 

 the square root of the length of the stroke, (art. 342.) l 



571. Owing to the escape at the valves and the disengagement of air, the 

 quantity of water a pump in the best order delivers at one stroke is, 



95 / a 2 x -7854 AACIO 72 v,- e 

 jjl = -00518 / a * cubic feet ; 



where / is the length of the stroke in feet, and a the diameter of the pump in 

 inches ; or substituting half the velocity for /, it gives the cubic feet per minute. 



572. The power required to raise water a given height is found by taking the 

 exact height in feet, from the surface of the water to the point of discharge, adding 

 one foot and a half for each lift, for the force required to give the water the velo- 

 city, and also one-twentieth of the height for the friction of the piston. Call this 

 quantity in feet h ; then -341 h a 2 = the load in Ibs. 



1 See note, page 167. 



