The Theory q/ Glacier motion. 143. 



Mr. Moseley requires, and the cross section of the ice plank 

 is 14 inches, it must require a pressure of i,05olbs. in order 

 to shear it. How then does it come about that it shears 

 under a pressure of 37^1bs ? The experiments shewed that,, 

 even if the whole weight of the plank were at work in 

 shearing it only along the supporting edges, instead of a por- 

 tion of it being taken off by the bearers and being otherwise 

 extended, it could not exceed 3 7 J^ lbs. for the whole area? 



which, for the two surfaces, would be ^-—^ or about i J^lbs. to 



the square inch {Phil. Mag., XLII. 333 — 4). 



In March, 1871, Professor Bianconi published a paper 

 in the Memoirs of the Bologna Academy ^ ser. III., vol. I. 

 p. 156, entitled, " Esperienze intorno alia flessibilita del 

 Ghiaccio." In this paper he refers to experiments which he 

 tried from 1866 onwards upon beams of ordinary ice 

 suspended on points and weighted in between. In these 

 experiments he found that the beam acquired a curved 

 flexure, and when it was reversed, and the weight 

 again attached, it curved in the opposite direction. In 

 another set of experiments he showed that after some hours 

 a beam of ice is susceptible of torsion. In other experi- 

 ments which he tried with granular ice, formed from 

 snow, the results were more marked. To his memoir are 

 attached plates in which the amount of bending and torsion 

 are shown. The general result is summed up in the following 

 words : Conchiudo, il ghiaccio possiede una flessibilita, o 

 pieghevolezza assai lente, ma bene spiegata, alia tempera tura 

 di -j-2, +3 etc. mentre rimane in ogni momento presente 

 la somma ma fragilita {pp. cit. 165). 



In the 4th volume of Nature Professor Tyndall published 

 some experiments he himself made on ice from the 

 Morteratsch Glacier in 187 1. In these experiments it was 

 clearly shown that a stout rectangle of clear and continuous 

 ice cut from the glacier, when properly supported and 

 weighted, showed signs of bending after twelvehours. Similar 



