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two ends of the meter, because there was a free communication 

 always open through the meter of larger area than the orifice of 

 the pipe through which the water was flowing away. He said that 

 the practical uniformity of measure was shown by the table of 

 trials of the meters, the limit of error allowed being about 2 per 

 cent. ; they were made to register a little too much at the lowest 

 speed, which was effected by increasing the drag-vanes beyond 

 what was strictly necessary to counteract the tendency of the 

 orifices in the propeller to form joints ; it being manifest that the 

 resisbance of the drag-vanes, like the force of the jets, would 

 increase as the square of the velocity. 



The Chairman inquired whether the meters had been employed 

 in regular use for both high and low pressures, and whether they 

 were found to register correctly in both cases ? 



Mr. Siemens replied that many of them were at work under both 

 circumstances, and no difference had been found in their measuring 

 from being worked under different pressures from 300 feet to 1 foot 

 head of water. 



There was always a grating fixed which prevented the entrance 

 of anything into the meter that would be liable to interfere with 

 its action ; and the smaller size of meters had a tubular grating (a 

 specimen of which was shown), giving a surface of grating much 

 more extended in proportion, which could be easily got at to 

 remove the deposits whenever they had accumulated sufficiently to 

 obstruct the water. . 



As to the expense, he thought for the smallest class of houses, 

 consuming only 100 gallons per day, Parkinson's meter would be 

 the cheapest, if the necessity for a cistern and the ascending 

 supply-pipe which it involved were not taken into account ; but 

 water meters were scarcely applicable to cases of such small supply. 

 The smallest size made, J inch bore, would supply 300 gallons per 

 hour, and cost 3 10s., a 1 inch meter, for 1200 gallons per 

 hour, 5 5s., and a large 10 inch meter, to deliver 100,000 

 gallons per hour, cost 50 or 60. 



The amount of pressure was balanced in every part, as the upper 

 oil vessel was also under the pressure ; and the extent of reduction 

 of the motion was so great, that no perceptible effect of friction 

 could arise on account of the great leverage, the drums in the 

 water having 20,000 revolutions for one of the index. A great 



