DUTY AND MEASUREMENT OF WATER. 123 



mulu is used : Total number of revolutions divided by 

 the time equals the revolutions per second. Total dis- 

 tance divided by the time equals the velocity in feet per 

 second which the meter moves through the water. Ve- 

 locity in feet per second divided by the number of revo- 

 lutions per second equals the ratio. 



The Water Register. This is a device used in 

 measuring the water that flows in specified currents suc'h 

 as rivers, canals or flumes. Figure 43 gives a very good 

 idea of its mechanism. 



FIG. 43. WATER REGISTER. 



It consists of a dial divided circumferentially into 

 spaces corresponding to the days of the week and the 

 hours and minutes of the day. Beginning at the cir- 

 cumference and going toward the center of the dial it is 

 divided into a scale of feet and inches. The dial is 

 turned by clockwork, making one revolution in seven 

 days. Pressing against the dial is a pen filled with a 

 specially prepared ink which does not dry in the pen. 



