72 



TIiA^'SACTIONS OF THE AjIERICAN LXSIITUTE. 



the slower movement of the first index of the register, and it required 

 practice to stop that index exactly in the same place at all times ; 

 hence a wide difference between contiguous records may be due to 

 imperfect manipulations, which would make no practical difi'ereuce 

 on the whole average. 



The results of the trial are shown in the followins; table : 



The first three trials were made at speeds sloicer than the 

 meter was ever required to run. during the engine tests^ and might, 

 therefore, be excluded. Their object was simply to find the maxi- 

 mum variation, the stream in one case being of less size than a 

 common lead pencil as it issued without force from the end of the 

 discharge pipe. The meter had openings two inches in diameter. 

 Tlie speed of the meter during most of the remaining six trials 

 was slower than the average speed during the engine tests for the 

 reason that the Croton " head " was too much reduced to deliver 

 through the meter without the assistance of the pump much more 

 water than an amount equal to that required during those experi- 

 ments. The tests marked " moderate " in the last column show the 

 rate of the meter during the trials of the engines. The meter had a 

 different rate for every considerable variation in speed ; but it did not 

 leak, for the water delivered at the slowest speed weighed the least. 

 At the slow speeds, therefore, the pistons did not quite complete 

 their strokes. The maximum variation from the average of the last 

 six tests was for a single owe of the slow tests two and a half per cent. 

 The others varied much less. During the trial, however, no such 

 variation as this could have taken place, for it is well known that the 

 rate of a meter is always the same at the same speed of discharge, 



