100 Rev. C. Trotter. Physical Properties of Ice [Jan. 29, 



some lateral pressure, and the bar had melted irregularly. The 

 holes c, e, had been made too near the shearing surface ; the ice 

 appeared a good deal crushed, and the holes were not recognisable 

 with certainty. If the holes were rightly identified the shear was 

 about 0'5 cm. The middle hole d was uninjured, the shearing sur- 

 face had been reduced by melting and shearing to about 35 X 2*5 cm. 



Shearing force at beginning of experiment 555 grm. per sq. cm. 



end „ 1430 „ 



(3.) July 16, bar and weight same as in (2). Examined July 19 ; 

 bar in good condition, shear probably about '05 cm. The weather on 

 July 16 had been very bad, and the holes had been rather hurriedly 

 and carelessly bored and measured, so that the final measurement of 

 the shear was not quite trustworthy. 



Shearing force at beginning of experiment 555 grm. 



I believe that the shear in (2) was rightly measured, but that it 

 had taken place chiefly after the bar had been considerably reduced 

 by melting, and the shearing force per sq. cm. considerably increased. 



In the course of the above preliminary experiments I came to the 

 conclusion that it was desirable to make use of a larger bar, and to 

 carry on the experiment for a longer time. I accordingly had a fresh 

 set of blocks made with holes 11 cm. square. The middle block was 

 10 cm. thick, the side ones 5f . 



A bar of ice was cut from a freshly excavated block and carefully 

 prepared. Two rows of three holes were bored in it, and the position 

 of the centre hole of each row carefully verified. Cork plates were 

 introduced between the ice and the wood on all sides. The apparatus 

 was hung up on July 18, and left undisturbed till August 4. 



Bar 11*5 X 10*5 cm., weight 48 kilos. 



On examining the bar on August 4 the holes were found in perfect 

 condition, the melting had been slight and regular. The thickness of 

 the bar had been reduced from 10' 5 to 10 cm. There had been 

 rather more melting where the pressure was applied, so that the 

 ultimate depth along the planes of shearing was ] 0*5 cm., so that the 

 final shearing surface was 2x10x10*5 = 210 sq. cm. The measure- 

 ments of the two rows of holes agreed well, and gave a shear of 

 •075 cm. 



Shearing force at beginning of experiment 199 grm. per sq. cm. 

 end ' „ 229 



I should have been glad, had time permitted, to have repeated and 

 varied the experiments further ; but I can feel no doubt that in the last 

 experiment a distinct shear of an amount not very different from 

 that wlych I have given, had taken place. The measurements were 



