286 THE SCIENTIFIC PAPERS OF 



sealed close, leaving only an eye in the centre through which an 

 upright stud of bronze B enters, which with its steel point abuts 

 against a steel plate in the bottom of the propeller. The lower 

 chamber F of the counter is formed of a white metal casting, cast 

 in one piece with the grating H, and filled completely with oil. 

 The arrangement of the counter itself is precisely similar to that 

 before described. 



Theoretically speaking, this meter is less perfect than the com- 

 pensation screw meter, but it possesses the great advantage 

 of containing only a single bearing, at C, that is at all liable 

 to wear, and that bearing is effectually protected from the 

 action of the water. The practical effect of this simplifica- 

 tion of parts has been, that of 150 meters of this description 

 that are at work, not one has as yet been returned disabled or 

 inaccurate. 



Mr. Adamson, of Leeds, has lately projected a meter with two 

 sets of spiral blades, upon the principle of a turbine, the inner set 

 being stationary, and the outer set revolving ; this meter also gives 

 a very good result. 



Another kind of meter lately brought out by Mr. Taylor, of 

 Manchester, having a revolving horizontal drum or water-wheel, 

 acts partially by jet and partially by impact, but on this account 

 it appears to the writer imperfect in principle. 



It has been argued before, that no accurate measurement can be 

 effected by the application of jets. To avoid them in the spiral 

 meter, it is essential to make the area of the outlet larger than 

 the area of the supply pipe. Nevertheless the nature of a jet still 

 manifests itself to some extent by increasing the rate of the meter 

 at high velocities. This defect has however been effectually coun- 

 teracted by the application of rotating flies or drag boards L L, 

 which offer a resistance increasing as the square of the velocity, 

 and can be regulated to equal the effect obtained by the jet. They 

 offer also great facility in adjusting the absolute measurement of 

 the meter. 



In order to insure the efficiency of each meter, it is necessary to 

 test the same under variable pressures, and with considerable 

 volumes of water. To this point the manufacturers, Messrs. Guest 

 and Chrimes, have devoted great attention. The apparatus they 

 employ consists of a large cistern, 40 feet high, and a second cis- 



