164 ROYAL SOCIETY OF CANADA 



Attention is directed — in Fig. 7 — to the manner in which the water 

 had cleaned the frazil from this rack at and below the water line although 

 the temperature of the air when the picture was taken was still much 

 below the freezing point. 



It is common practice at hydraulic plants, other than water-supply 

 and hydro-electric stations, to let the sun thaw the plants out, next day, 

 after frazil shuts them down ! No effort is ever made to start ordinary 

 mills up again during the same night that frazil shuts them down. With 

 the operators of water, electric light and power services, however, other 

 practices must of necessity obtain. The work of attempted relief is 

 immediately begun. The members of the medical profession are not 

 alone in having their night's rest disturbed. 



Fig. 8 shows how relief from frazil attacks was afforded to the 

 hydro-electric power plants in the Ottawa district during the two decades 

 preceding the winter of 1905. A simpler and speedier method has since 

 come into use at a majority of these and some other plants. When 

 the water-wheel gates became frozen, the chutes clogged up, the pen- 

 stocks filled, and, the racks blocked with frazil, it was formerly neces- 

 sary for workmen to remove these icy accumulations by hand, or, to 

 wait for next day's sun. As the frazil was crystallized as soon as it 

 came into contact with the cold air, it was necessary to break it up with 

 bars and axes before it could be taken out of the wheel pit. More 

 than half the accumulation of frazil fro7n this wheel pit had been 

 removed when the picture was taken. After the ice was removed one 

 of the following courses had to be adopted to loosen the gates which 

 were still frozen to the wheel-cases: — (1) Either liberal doses of 

 brine had to be applied to the gates, or, (3) a fire of oily waste and kind- 

 ling wood had to be built around the wheel-case for the purpose of 

 actually melting the ice and loosening the gates. Steam was sometimes 

 used for melting the ice when it was available. 



This ice-cleaning-out and ice-melting process usually occupied from 

 three to five hours, the length of time depending upon the amount of 

 ice to be removed, and, the difficulty of getting down and up the head 

 gates or stop logs; — the latter, when put down, frequently froze in posi- 

 tion and another difficulty was thus placed in the way of quickly re- 

 starting the plant. 



It is almost out of place to mention that absolute continuity of 

 supply is a necessity in connection with electric light and power services, 

 and that a shut-down of one minute's duration is an unpardonable 

 occurrence. Keeping this point in mind consider the effect of a 

 five-hour or a fifteen-Jiour shut-down! Tliese lengthy shut-downs came 



