[barnks] TEMPERATURE OF THE LACHINE RAPIDS 27 



of ice and water depends on the relative amounts of ice or water present, 

 has also been stated. The experiments conducted by the writer, although 

 not undertaken to show any such supposition, yet indirectly support this. 

 The fact that in the measurements of the temperature of the water under 

 the surface ice, the water commenced, after a sudden cold dip, by being in 

 a slightly undercooled state, and that after the proportion of ice increased, 

 the temperature gradually came to the freezing-point, wotdd tend to show 

 this. In the open water, where the quantity of water is very great, 

 compared to the ice, a slightly larger ditference has been observed than 

 was possible under the ice. Although the more the water is being 

 churned up and mixed with air and ice, the less can its temperature 

 be cooled below the freezing-point. It has been shown in the writer's ex- 

 periments that radiation must be an important factor in the manufacture 

 of river ice. This has been often disputed, and for that reason it was sat- 

 isfactory to have been able to actually demonstrate it by the effect on the 

 stem of the thermometer itself. Another important indication of radiation 

 is that the ground ice apparently grows on dark rocks easier than on 

 light ones. 



On the Formation and Agglomeration of Frazil and Anchor Ice. 



The terms "frazil" and "anchor ice" appear to be often under- 

 stood as the French and English for the same thing, both referring to the 

 ice formed on the bottom of a river. Frazil has also come to be applied 

 to the fine surface crystals to be found throughout the mass of a river, on 

 account of the widely held opinion, which is undoubtedlj^ correct in part, 

 that ground ice is formed by the sticking on the bottom of these tine needle 

 crystals. Accepting the obvious action of radiation in causing ice to grow 

 in situ on the bed of a river, it appears to the writer that some distinguish- 

 ing terminology should be applied. Already, in the report of the Mont- 

 real Flood Commission, published in 1890, which is the highest authority 

 on river ice formation we have, will be found the following : "Frazil, as 

 distinguished from anchor ice, is formed over the whole unfrozen sur- 

 face above and below Lachine Eapids, between Prescott and tide water, 

 and wherever there is sufficient current or wind agitation to prevent the 

 formation of bordage ice . . ." This distinction appears to the writer to be 

 a fair and natui'al one, accepting, of course, the already obvious and ex- 

 clusive meaning of anchor ice. 



The connection between the two forms of river ice lies in the fact that 

 during extreme cold weather, when the water becomes slightly under- 

 cooled, there is a large excess of frazil being formed. Lower layers of 

 these crystals and quantities carried to the bottom by the surface currents 

 become attached to the anchor ice, and help to build it up. "Whether or 

 not the frazil could become attached to the bottom previous to the for- 

 mation in situ of a layer of ground ice, .seems doubtful. 



