[murphy] the ice QUE.S1I0N 163 



becomes uncoDtrollable ! Tlie automatic governors, although very power- 

 ful machines, are not capaljle of loosening frozen gates from their icy 

 grip and heavy gearing is often broken in the attempt. It is 

 a common occurrence to see steel pinions having large factors of 

 safety, so far as mechanical strength is concerned when doing their 

 ordinary work, torn apart while an effort is being made to loosen water 

 wheel gates which have become fastened to the wheel cases by frazil. 

 The freezing of the controlling gates of a water power plant is a more 

 serious matter than is generally realized ; a plant might, in this condi- 

 tion, be compared to a runaway locomotive but for the fact that the 

 locomotive, awful though its destructive capabilities may be, cannot do 

 nearly so much damage as the runaway power plant. The energy of the 

 locomotive is reckoned in hundreds of horse power while the power 

 plant's capacity is usually measured in thousands ! The fire may be 

 drawn, or, it will soon die out under the boiler of a runaway locomotive, 

 but a river is not likely to stop its flow within the same time-limit. If 

 the load which is being cari-ied by a power plant falls oil' while the con- 

 trolling gates are frozen to the wheel-case disastrous electrical and me- 

 chanical breakdowns may follow. One not intimately acquainted with 

 these conditions can scarcely imagine the serious plight in which a 

 power plant and its attendants are placed when the controlling gates 

 become frozen tight and the speed of the apparatus gets beyond control. 



(3) The third difficulty to which frazil subjects a power plant is 

 the clogging up of the water-wheel chutes. The effect of ice closing up 

 the chutes is just the same as closing the gate and a complete shut-down 

 is thus effected. 



The top part of the rack, in Fig. 7, to which frazil is clinging may 

 convey some idea of the manner in which frazil will plaster up a rack 

 and prevent water from entering the wheel pits or penstocks. All the 

 mills and power houses in the Ottawa district were stopped by frazil on 

 the occasion when this picture was taken and, as the water in the head 

 races arose when the plants were stopped, this accounts for the lieight to 

 which the frazil ascended this rack. Frazil covered every portion of this 

 rack from top to bottom to such an extent that not a drop of water could 

 pass through it. When this picture was taken, the plants were all again 

 in operation and the water in the forebay had dropped to its usual height. 

 The sun had relieved this plant. This rack faces the South. Eacks 

 facing the North freeze up more quickly and remain frozen longer. This 

 valuable point seems to appeal more strongly to greenhouse designers 

 than to the designers of some water-power plants. 



Sec. III., 1009. 10. 



