282 THE SCIENTIFIC PAPERS OF, 



G, carrying a pinion X, which is geared into two wheels Y and Z, 

 of equal diameters, but the former with 101, and the latter with 

 100 teeth. The wheel of 101 teeth carries a large dial plate 0, 

 divided in its circumference into 100 equal divisions ; and the 

 wheel of 100 teeth is fixed upon the upright spindle, and carries a 

 hand Q, upon the dial. The dial in travelling through the breadth 

 of one division under a fixed pointer is intended to indicate the 

 passage of 100 gallons through the meter. For every one com- 

 plete revolution of the dial, the hand advances relatively through 

 the breadth of one division, signifying the passage of 100,000 

 gallons. The millions of gallons are indicated on a separate circle 

 of divisions on the large dial, by a hand R, which receives a 

 reduced motion by a wheel S of 100 teeth rotating bodily with the 

 dial, gearing into a pinion of 10 teeth, fixed to the upright 

 spindle. 



The dial face is exposed to view through the cover of plate 

 glass I. 



The water enters the meter through the grating P. which is pro- 

 vided to arrest large solid bodies that might obstruct the working 

 of the meter. The inverted cone R directs the current of water 

 toward the centre, where it again spreads over the conical block 

 H, and being directed parallel to the axis between the guide vanes 

 K it impinges obliquely upon the right-handed vanes of the 

 hollow screw drum E. The object of (figuratively speaking) 

 kneading the current of water between the conical surfaces, is to 

 destroy partial currents within the same, and in spreading it from 

 the axis to increase its leverage on the rotating drum ; the 

 diameter of the body of the drum is made slightly smaller than the 

 diameter of the conical block, in order to prevent the former from 

 endway pressure of the moving column of water. Some clearance 

 is allowed between the helical vanes and the surrounding casing, 

 but the passage of water outside the vanes is effectually prevented 

 by slight contractions of the water way at both ends. In order to 

 prevent wear and friction on the bearings, the body of the 

 revolving drum is made hollow to such an extent that the water 

 displaced nearly balances the weight of metal. A screw drum of 

 this description moves with a very gentle current of water, but it 

 would, nevertheless, make a very imperfect meter if it were simply 

 connected to the counter, inasmuch as the friction in the bearings 



