1 88 



PUMPS AND THEIR VALUE TO MAN 



surd if employed on our huge vessels of war and commerce. 

 Here a rent in the ship's side would mean inevitable loss 

 were it not possible to rid the ship of the inflowing water by 

 the action of strong pumps. 



Another and very different use to which pumps are put is 

 seen in the compression of gases. Air is forced into the tires 

 of bicycles and automobiles until they become sufficiently in- 

 flated to insure comfort in riding. Some present-day sys- 

 tems of artificial refrigeration (Section 93) could not exist 

 without the aid of compressed gases. 



Compressed air has played a very important rdle in mining, 

 being sent into poorly ventilated mines to improve the condi- 

 tion of the air, and to supply to the miners the oxygen neces- 

 sary for respiration. Divers and men who work under water 

 carry on their backs a tank of compressed air, and take from 

 it, at will, the amount required. 



There are many forms of pumps, and they serve widely 

 different purposes, being essential to the operation of many 



industrial undertak- 

 ings. In the follow- 

 ing Sections some of 

 these forms will be 

 studied. 



182. The Air as 

 Man's Servant. Long 

 before man harnessed 

 water for turbines, or 

 steam for engines, he 

 made the air serve his 

 purpose, and by means of it raised water from hidden under- 

 ground depths to the surface of the earth; likewise, by 

 means of it, he raised to his dwelling on the hillside 

 water from the stream in the valley below. Those who 



Fl(~. 131. Carrying water home from the spring. 



