354 



Messrs. J. C. McConnel and D. A. Kidd. [June 21, 



The area of section was 6 sq. cm., and the tension 4 kilos, per sq. cm. 

 The measurement was taken with glass indicators. A long straight 

 glass fibre was used as indicator, bent at one end to hook under the 

 lower needle, and supported in a nearly horizontal position by a glass 

 connecting fibre hooked over the upper needle. The vertical scale 

 was attached to an arm projecting from the upper iron plate. 



During the first 22'5 hours the ice extended 3*7 mm. on the outer 

 side, and contracted 0*75 mm. on the inner side. During a sub- 

 sequent six hours it extended 1*7 mm. on the outer side and 0"6 mm. 

 on the inner. The mean rate per hour per length of 10 cm. was 

 therefore 0*046 mm. The temperature is not known with any 

 certainty. This ice was never examined under the polariscope, but 

 owing to the mode of formation described fully at the end of the 

 paper, we may be certain the structure was in the highest degree 

 irregular. It was probably, however, tolerably symmetrical about 

 the axis, so the bending may be attributed to the eccentric application 

 of the pull. 



Experiment No. 4i. Bough Apparatus. — The specimen was a piece of 

 glacier ice (A), composed of perhaps a dozen "grains" very 

 irregularly arranged, the axes of some being at right angles, of 

 others parallel, to the length. Distance between needles about 22 cm. 

 The area of the section is a little uncertain, as it was not measured 

 in situ, and the ice was not protected from evaporation. It may be 

 taken as 6*5 sq. cm., and the tension as 1'66 kilo, per sq. cm. The 

 ice was subjected to tension for about eighty-five hours altogether, 

 but we only give the results for the last twenty-seven, as at first the 

 indicators appear to have slipped, and, after precautions had been 

 taken to prevent slipping the two indicators happened to come in 

 contact. The indicators were arranged as in the last experiment, but 

 the readings were improved by attaching a mirror to the scale. The 

 multiplication was about 30, and the extensions may be trusted to 

 0*03 mm. The first column in the annexed table gives the time of 

 each reading, the second the temperature at that time, the third the 

 interval between two readings, the fourth and fifth the actual 

 extensions measured by the outer and inner indicators in that 

 interval, and the sixth the rate per hour per length of 10 cm. 



The temperatures are somewhat uncertain, as the ice was not 

 enclosed in a box, and the temperature of the room was very far 

 from being uniform. The last four temperatures were taken by a 

 thermometer hung close by the ice and on the same level. The 

 minimum of the night by this thermometer was —3*3°. The high 

 temperature at 21 h. 15 m. was due to the window of the room having 

 been nearly closed. It was then thrown wide open, so the temperature 

 must have soon fa^en again. So the interval before this reading, 0*0°, 

 would probably be much warmer on the average than the subsequent 



