PUMPING WATERS. IOI 



pump. This would prevent damage to the pump in 

 case it was started against a closed valve on the dis- 

 charge, an occurrence of which, due to a careless 

 workman, was witnessed by the writer to his physi- 

 cal discomfort. 



As the subject of internal combustion engines is so 

 important in the case of small water supply schemes, 

 it may be well to say a few words on them for the 

 benefit of those who have little or no experience in this 

 connexion, and who would perhaps otherwise be at the 

 mercy of the engine builders. Of course it pays to 

 deal only with high-class firms, who would rather help 

 and advise than take advantage of the inexperienced. 



The bed of a gas engine (under which heading are 

 included oil and spirit engines) similar to that shown 

 in fig. 77 is of cast iron. The cylinder is a separate 

 casting and is generally in one with the combustion 

 chamber and exhaust valve box. Ample space 

 should be provided for the circulation of cooling 

 water around the walls and valve seats most exposed 

 to the high temperature of the explosions. The 

 cylinder should be fitted with a removable liner of 

 very hard metal which can be easily replaced at any 

 time. The crank shaft and connecting-rods are of 

 mild steel. The former should be made from one 

 forging with the throw slotted out and run in long, 

 gun-metal adjustable bearings. 



In oil engines the ignition may be effected by 

 either an externally heated tube of nickel alloy 

 heated by a wickless lamp adjusted in relation to the 

 tube, or an internally heated tube of nickel alloy en- 

 closed in a small chamber filled with non-conducting 

 material. 



