18 THE ROYAL SOCIETY OF CANADA 



The results are of interest as representing forces actually exerted 

 by the ice, although they do not give the theoretical maximum thrust, 

 which according to accepted notions, would equal 28,800 pounds per 

 linear foot for ice only half as thick. This bears out our ideas of the 

 yielding of ice below the crushing strength. 



Mr. Bell states: "The crushing strength of floating ice may be 

 taken at about 10 tons per square foot. 



"A bridge pier was shifted by a blow from a large field of ice, 

 and the crushing strength of the ice was figured from the force necessary 

 to replace the pier. This was 1 1 tons per square foot. 



"A careful study of ice reefs and the maximum thickness of 

 the ice at which they form in any locality, together with experiments 

 on long columns of floating ice in the water, would furnish much valu- 

 able data. From the present limited data, the writer believes that a 

 dam exposed to the full pressure of ice should be designed to resist 

 from 43,000 to 48,000 pounds per linear foot, and that structures 

 subject to blows from floating ice should be capable of resisting from 

 10 to 12 tons per square foot, on the area exposed to the greatest thick- 

 ness of floating ice." 



Experiments made by Mr. Bell on the adhesion of ice frozen 

 to concrete surfaces is of much interest and importance. He states: — 



"These tests indicate that if ice is firmly frozen to the concrete, 

 it will develop its full crushing strength, irrespective of the inclina- 

 tion of the line of ice to the surface of the concrete, as long as the 

 temperature of the ice is below the freezing point. 



"William M. Patton, in his treatise on foundations, says that 

 the adhesion of ice to a pier, even to the sloping surface, may be so 

 great as to develop the full crushing strength of the ice. 



"When the natural upper surface of the ice was perpendicular 

 to the line of thrust, the samples fractured horizontally and verti- 

 cally, when the natural upper surface was parallel to the line of thrust, 

 the samples fractured in parallel vertical planes only. 



"In the latter case, if the ice had reached a temperature of thirty- 

 two degrees, it was often impossible to obtain further signs of failure, 

 as the ice under the pressure of five or six hundred pounds per square 

 inch, would spread or flow without further fracture." 



Conclusions. 



As a result of our study of ice expansion which must be regarded 

 as only preliminary, we find that — 



(1) The crushing strength of ice is most probably 400 lbs. per 

 sq. inch, or 28 kilos per sq. cm. 



