Intelligence and Miscellaneous Articles. 335 



In another series of experiments, the temperature of the air being 

 _ V> 0., various hollow iron cylinders, and a solid piece of steel 

 whose base had a surface of exactly 1 square centim., were placed 

 upon ice, and this was then covered with snow to the height of 

 about 1 foot. With a pressure equal to -J- of an atmosphere upon 

 a steel piece of 64 centims. superficies it sank in 3 hours 14 millims. 

 into the ice, while the melting away of the surface during that time 

 was barely measurable, amounting to | millim. The quadrangular 

 solid prism of steel, exerting a pressure of 3 of an atmosphere, sank 

 4 millims. in 5 hours. It appears very clearly from all these ex- 

 periments how considerable becomes the yielding of the ice itself 

 to the slightest pressure with a temperature near its melting-point. 

 AVe may hence infer that, at this temperature, the plasticity of ice 

 sinks to zero only when the pressure likewise becomes nil, but with 

 falling temperature falls very rapidly. To ascertain, however, in 

 what ratio this ensues, a greater number of precise experiments 

 than I have made would be needed. 



It is still constantly assumed, on the ground of some of Tyndall's 

 experiments, that ice is destitute of extensibility and flexibility, al- 

 though repeated observations recently made compel us to ascribe to 

 ice some flexibility. The oldest observation of this kind known to 

 me originated with Kane, who remarked that a large lump of ice 

 with its edges resting on two others became curved in the course of 

 some months. 



I made several experiments in a similar manner to that, in which 

 nature had operated previously to Kane. A parallelepiped of ice 

 52 centims. long, 2-5 wide, and 1*3 thick was placed with its two 

 ends to the extent of 5 millims. resting on blocks of wood. Erom 

 the 8th to the 15th of February, the temperature varying between 

 — 12° and 3° # 5, the centre sank extremely little, yet decidedly per- 

 ceptibly, from day to day, on the average from 2 to 3 millims. in 

 24 hours ; so that the total sinking amounted on the 15th to 11*5 

 millims. From that time the temperature rose, but remained below 

 zero till noon of the 16th ; yet even this rise of temperature effected 

 a quick increase of the flexure, as in 24 hours (from 8 a.m. on the 

 15th to the same hour on the 16th) the latter reached the 

 amount of 9 millims. (consequently 20-5 in all). No rending 

 of the ice was anywhere perceptible ; even the under surface did 

 not, on the most careful examination, show the minutest trace 

 of a crack. Up to 2 o'clock t.M. the sinking increased 3 millims. 

 The next inspection, at 5, during which time the temperature had 

 risen to +3°, showed the bar broken into two pieces. 



Consequently, at the last observation, the bending in a perpen- 

 dicular direction (that is, the height of the perpendicular erected 

 upon the chord of the arc at last formed by the ice) amounted to 

 23*5 millims., which certainly, considering that the length of the 

 chord was but 51 centims., must be called very considerable, and at 

 all events proves that ice is not so unyielding towards stretching 

 and pull, provided this acts with sufficient slowness. 



I next endeavoured to determine the amount of extension of ice 

 by traction. To n prism of ice of the same dimensions as that em- 



