I04 



NA TURE 



[June 4. 1908 



The sun's rays are effective in detacliing the anchor- 

 ice from the bottom. On a clear morning in winter, 

 as soon as the sun rises, the open surfaces of the St. 

 Lawrence become dotted over with large masses of 

 anchor-ice, which rise high out of the water by the 

 impetus thev attain, and sinli back with a character- 

 istic noise. Large boulders frozen to the masses are 

 frequently brought up and carried in the currents. 



I'm 



-Anchor-ice grown up from the rocks and protruding above the surface of the Ottawa river. 



water-level where 



When the day is cold and cloudy, anchor-ice does not 

 rise, but builds from the frazil in the water. 



Boatmen are careful not to cross the river when 

 anchor-ice is rising for fear of having a mass come 

 up under the boat and carry it helplessly into a rapid 

 or over a waterfall. 



The limit of depth below the 

 anchor-ice will form appears to be 

 roughly about 40 feet, but in the 

 clear waters of the Gulf of St. 

 Lawrence it has been observed as 

 deep as 70 feet. Twenty feet 

 below the surface, anchor-ice will 

 often attain a thickness of 5 or 

 6 feet during prolonged cold 

 weather. When seen through 

 the water, the growth resembles 

 nothing more closely than the 

 weeds that are found in the shal- 

 lower portions in summer. Anchor- 

 ice grows in arborescent forms, 

 and with more abundance on 

 dark-coloured rocks, although 

 when it becomes very thick the 

 radiation takes place chiefly from 

 the ice-surface itself. During mild 

 weather, especially with rain, 

 practically all the anchor-ice is 

 detached from the bottom, and 

 this has been shown to accompany 

 a slight temperature elevation in 

 the water above the freezing point. 



Fig. 2 shows an ice bridge on the Ottawa River 

 in the process of formation. The anchor-ice may be 

 seen protruding above the water in the shallower parts, 

 and frazil-ice may be seen floating in the current. 



Fig. 3 shows the spillway and waste weir of a large 

 power station. .-Xnchor-ice to which frazil has adhered 

 may be seen under the water surface and in places 

 protruding above. The thickness of ice on the crest was 



NO. 2014, VOL. 78] 



from 18 to 22 inches at the time the photograph was 

 taken. In the background men may be seen with long 

 rakes scraping the frazil-ice off the rack-bars or screen 

 through which the water passes to the turbines. 



When turbines are operated under very high heads, 

 the supercooling of the water is corrected by the heat 

 generated during the fall and the lowering of the 

 normal freezing point by pressure. Power-houses so 

 situated are seldom troubled with 

 adhesive ice. Many power-houses 

 are fortunately situated so thar 

 water is drawn from deep ice- 

 covered channels, where frazil or 

 anchor-ice cannot form, but for 

 nearly all there are times, at the 

 outset of cold weather, before the 

 surface-ice forms, when trouble is 

 encountered. For these and for 

 all water-works situated belov/ 

 permanently open water, steam or 

 electric heating must be resorted 

 to at times, if interruption to the 

 operation is to be avoided. 



Through the good work of Mr. 

 John Murphy, M..'\.LE.E., of the 

 Department of Railways and 

 Canals, Ottawa, practical and 

 effective devices are now available 

 for overcoming ice troubles, and 

 in place of expensive auxiliary 

 steam plants for carrying the load 

 during the frazil season, with their 

 corresponding large consumption 

 of coal, a modest steam boiler, or a small amount 

 of electrical energy — usually available in excess 

 — proves an effective means of keeping the plant run- 

 ning smoothly. 



To the practical superintendent of a power-house the 

 idea of a thousandth of a degree has little meaning, 

 and yet there is no doubt that the ice problem, as it is 



1 he thickness of ice 



presented in the development of " white coal " in 

 northern countries, depends on just such minute 

 changes of temperature. 



It has been thought that the ice conditions in Canada 

 might detract from the value of the vast water powers 

 available for power purposes, but, from a scientific 

 study of the conditions underlying the formation of 

 ice, it is safe to say that no such bar exists. 



H. T. B.\RNES. 



