MECHANICAL AND USEFUL ARTS. 93 



"On Improvements in High- pressure Watar-meters." Mr. Chad- 

 ,wick stated, there were at the present time about 10,000 high- 

 pressure water meters in use in Europe, of which about one-half 

 were of the kind known as " inferential meters," Siemens's, 

 Adamson's, Taylor's, Mitchell's, and others ; the remainder being 

 "positive meters," working on the principle of the piston and cylin- 

 der, such as Kennedy's, Worthington's, Jopling's, Duncan's, and 

 Chadwick and Frost's. If no serious practical objection had hitherto 

 existed to the adoption of water-meters, it is within reasonable pro- 

 bability that the number now in use would have been 100 times 

 greater than it is. After reviewing the progress of invention as 

 regards these meters, Mr. Chadwick showed that from 1821 to 1S58, 

 84 patents had been taken out for water-meters ; of that number 

 it might safely be affirmed that not more than six or seven were 

 now in practical use, and only two in extensive use. Of inferential 

 meters only those of Mr. Taylor and Mr. Siemens have been exten- 

 sively used ; and although the latter was admitted to be an ingeni- 

 ous invention, its inventor admitted that undercertain circumstances 

 his meter would allow a certain small quantity of water to pass un- 

 measured. The principle of measuring by inference, however, from 

 the revolution of a wheel, spiral fan, or turbine, did not present to 

 the mind that conclusive evidence of exactitude which we were ac- 

 customed to demand in our dealings with other matters ; and this 

 feeling of uncertainty was increased when it was known that these 

 meters, even with the most perfect possible workmanship, must 

 allow a leakage varying according to the size of the meter, when 

 used under circumstances in which the velocity of the current was 

 insufficient to overcome the friction of the working parts of the 

 machine. 



Having pointed out the defects of some of the meters already in 

 use, Mr. Chadwick said that the new high-pressure piston water- 

 meter of Chadwick and Frost effectually overcame the difficulties 

 and objections he had noticed. It consists of a vertical cylinder and 

 piston with a reciprocating action. The cylinder is lined with brass, 

 and the piston packed with cupped leather. The piston rod passes 

 through a stuffing-box at the top of the measuring cylinder into a 

 separated valve chamber, to which there is no connexion with the 

 measuring cylinder except through the parts of a slide three-way 

 valve, the two ends of the moving part of which form pistons work- 

 ing in small cups or cylinders, and on the top of this valve a second 

 slide valve works. When the main piston has fully completed its 

 stroke, a projecting portion of the rod comes in contact with a catch, 

 which moves the top slide valve and admits the full pressure of the 

 water to one of the cups ; whilst it at the same time opens a way for 

 the discharge of water from the opposite cup, and the pressure so 

 exerted moves the main valve by which the flow of water is reversed 

 and directed into the other end of the measuring cylinder until the 

 completion of another stroke, when the like motion is again re- 

 peated. The opening of the top valve to admit the water to the 

 small cups at the completion of each stroke entirely prevents all 



