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NEW YORK STATE MUSEUM 



terms " frazil " and " anchor ice " have been used synonymously, 

 and are apparently often understood as the French and English 

 words for the same thing, but the following from the report of 

 the Montreal Flood Commission of 1890 will serve to define the 

 difference. According to this report, frazil is formed over the 

 whole unfrozen surface wherever there is sufficient current or 

 wind agitation to prevent the formation of border ice; whereas 

 the term anchor ice includes only such ice as is found attached 

 to the bottom. Frazil is frequently misused by being made to 

 include ice formed on the bottom, as well as throughout the mass 

 and on the surface of a river, although properly it should be only 

 applied to floating ice. The common theory has been that anchor 

 ice first forms on the bottom, subsequently rising. The Montreal 

 studies, however, show that this is hardly true. At times the 

 whole mass of water from surface to bottom is filled with fine 

 needles which actually form throughout the water mass itself. 



As to the remedy, the studies are hardly complete enough to 

 indicate the best course to pursue. As practical hints, it may be 

 stated that in locating dams on streams specially subject to this 

 difficulty they should be placed with reference to as long a 

 stretch of backwater and as great depth as possible, all the 

 studies thus far made tending to show that the formation is most 

 extensive in shallow, rapid-flowing water. Usually, trouble from 

 frazil and anchor ice extends through a period of a day or two; 

 and at very important plants, where even a short interruption 

 would be a serious matter, arrangements may be made for using 

 steam at the headworks for keeping the racks open. This plan 

 has been successfully pursued at the waterworks intakes of several 

 of the Great Lake cities. In the case of power plants, where much 

 larger quantities of water are required and the stream flows with 

 greater velocity, the amount of steam required may be very large. 1 



x For literature of frazil and anchor ice see (1) Report of the Montreal 

 Flood Commissioners of 188G; (2) Reports of the Harbor Commissioners of 

 Montreal for the years 1885, 1887, and 1895; (3) Paper on Frazil Ice and 

 Its Nature, and the Prevention of Its Actions in Causing Floods, by George 

 H. Henshaw, Trans. Can. Soc. C. E. Vol. I, Part I, p. 1-23; and (4) Paper 

 on the Formation and Agglomeration of Frazil and Anchor Ice, by Howard 

 T. Barnes, in Canadian Engineer, Vol. V (May, 1897). 



