[murphy] 



THE ICE QUESTION 



1S8 



of our crude work and the accurate and excellent work of Dr. Barnes to 

 which I refer below. 



Now that we have seen how and when frazil is formed a view of a 

 water power plant — as in Fig. 3 — may assist in obtaining a better un- 

 derstanding of the troubles which frazil causes to it. 



Fig. 3 is a sectional view of a horizontal water-wheel and wheel-pit. 



A is a view of one bar of the rack, or screen, which prevents float- 

 ing debris from being carried into the penstock or wheel pit. The rack 

 bars are set at a slight angle for cleaning or raking purposes. The dis- 



O'F. 



/\iV=0°F. 



Fig. 3. 



tance between these rack bars varies from 1 to 3 inches according to the 

 sizes of the openings in the wheels which thej^ are to protect. 



B is the wheel-pit in which the complete water-wheel outfit is set up. 



C is the wheel case in which the water wheel or turbine D runs. 



C^ C^ are the chutes between which the water passes as it enters the 

 wheel. 



C^^ is a cylinder gate by means of which the water-wheel is started, 

 stopped and controlled by varying the length of the opening between the 

 end of the ffate and the wheel case and thus controllino: the amount of 



