A SUGGESTED METHOD OF TEST 149 



pressure on the pressure gauge, which should always show a 

 constant reading) and the throttling gate slowly opened until 

 the moving parts of the meter commence to revolve. It 

 would then be closed down until they stop, and then opened, 

 watching the manometer closely, as far as possible without 

 again starting them. The manometer reading and the corre- 

 sponding quantity should be then entered in the record as 

 the quantity that will pass with no registration. The con- 

 trolling valve should then be opened until the moving parts 

 move very slowly, the observation repeated, but this time with 

 the addition of a record of the rate at which the meter is record- 

 ing. Opening it further, the operation should be repeated at a 

 number of points as may be indicated by experience. 



In making up the record in tabular form, it is suggested that 

 the slip should be calculated in every case; that is to say, the 

 difference between the actual quantity of water passing and 

 the quantity indicated by the meter. 



For plotting, logarithmic paper should be used, and a 4-inch 

 or 5-inch base will be sufficient. The quantity in gallons per 

 day should be shown in one direction and against this should be 

 plotted the amount of slip ascertained for those quantities. 



This method of testing involves the use of the slide rule for 

 rapid calculation, but there are no greater difficulties in the 

 calculations or in making records than are common in hydraulic 

 and laboratory work. With such equipment once installed and 

 tested out, it would seem possible to put a meter through all of 

 its paces and ascertain substantially what it is capable of doing 

 at low rates in a very few minutes. 



Testing old meters of various types after they have seen 

 some years of service will be most likely to be productive of 

 useful ideas as to types and materials giving continued suc- 

 cessful registration. 



The following is a suggestion for a further specification for 

 meters in connection with these tests: 



" The slip of the meter at low rates shall not exceed - 

 gallons per twenty-four hours. When the moving parts are 

 stationary and water is allowed to flow through the meter at a 



