METHODS OF CONDUCTING THE TESTS. 15 



the time arrives on the next morning, corresponding to the time 

 when the test was started, the position of the water line and the 

 indication of the steam gauge shall be the same as at the begin- 

 ning. The last observation of the test is thus made 24 hours 

 after the time of the first observation, when the condition of the 

 boiler is presumably the same. If the water line occupies a 

 different position, a suitable correction is applied to the weight 

 of water measured, which is determined by computing the quan- 

 tity from the volume which it occupies, calculated from the 

 known dimensions of the boiler. If there is a difference 

 of pressure, no account is taken of it, unless the difference 

 is large ; in which case, the quantity of evaporation is computed 

 which would take place if the stop valve were opened and a 

 sufficient amount of steam let off to reduce the pressure from the 

 higher to the lower point. In conducting a test according to 

 this method, the small quantity of evaporation which takes place 

 during the night, produced by heat stored in the boiler at the 

 end of the day's run, is included in the total evaporation of the 

 test. 



During the progress of the test the feed-water is weighed 

 previous to its supply either to the pump or injector which 

 feeds it. The weighing apparatus consists of two tanks, one of 

 which rests on a platform scale, which is supported by staging 

 raised above the level of the other. The water is first drawn 

 into the upper tank. Here it is weighed and then emptied into 

 the lower tank. Thence it passes into the suction pipe of the 

 pump or injector, which is temporarily changed from its usual 

 connection for the purpose. 



All pipes connected with the feeding apparatus, except those 

 concerned in the work of the test, are disconnected ; and if this 

 cannot be done , the tightness of valves which must be depended 

 upon is first assured. If the blow-off valve leaks, it is plugged. 



In cases where an injector is used, and where there is no 

 heater connected with the boiler, the temperature of the water 

 is taken at its entrance to the lower tank. If a heater is used, 

 the temperature is taken at its entrance to the boiler, a ther- 

 mometer being set in the feed pipe for this purpose. If both 



