102 SMALL WATER SUPPLIES. 



The engine is started by an externally heated 

 tube and run for a short time, when the internal tube 

 gets sufficiently hot to run the engine without 

 further attention, the external tube being put out of 

 use. With producer-gas the magneto ignition is the 

 most efficient. 



^The governing of all but the very smallest sizes 

 (which employ an inertia governor) is effected by the 

 usual centrifugal form of governor on the hit-and- 

 miss principle. That is, when the engine exceeds the 

 normal speed the governor causes it to make an idle 

 stroke when otherwise it would make a power stroke. 



As before stated, it is most important for the 

 buyer to be quite clear on the point of "horse- 

 power ". 



No other definition of the term should be con- 

 sidered than the working Brake horse-power which 

 the engine will give off during an ordinary full day's 

 work of ten hours. 



Where it would not entail a long journey, a visit 

 to the works to see the engine working on the test 

 beds is very advisable, otherwise a test certificate 

 should be applied for, and in all cases a trial run 

 should be specified after the installation is fixed. 



The approximate consumption of oil in a first- 

 class engine should not exceed one pint per working 

 Brake horse-power per hour under normal condi- 

 tions when working at full load. In large engines 

 this will be reduced, while at partial loads it will be 

 increased for any engine. Hence the desirability of 

 working the engine up to its full load. In all cases 

 the brand of petroleum used should be that advised 

 by the makers for the particular engine. 



