and Motion of Glaciers. 367 



have been adduced by M. Escher in proof of the plasticity of the 

 substance, — are all calculated to establish the conviction, that 

 the mass must be either viscous, or endowed iviih some other pi'O- 

 perty mechanically equivalent to viscosity. The question then 

 occurs, is the viscosity real or apparent ? Does any property 

 equivalent to viscosity exist, in virtue of which ice can move 

 and mould itself in the manner indicated, and which is still in 

 harmony with our experience of the non-viscous character of the 

 substance ? If such a property can be shown to exist, the choice 

 will rest between a quality which ice is proved to possess, and 

 one which, in opposition to general experience, it is assumed to 

 possess, in accounting for a series of phsenomena which either 

 the real or the hypothetical property might be sufficient to pro- 

 duce. In the next section, the existence of a true cause will be 

 pointed out, which reconciles the properties of ice, exhibited even 

 by hand specimens, with the apparent evidences of viscosity 

 already referred to, and which, though it has been overlooked 

 hitherto, must play a part of the highest importance in the phse- 

 nomena of the glacier world, 



§ 3. On the Regelation of Ice, and its application to Glacial 

 Phenomena. 



In a lecture given by Mr. Faraday at the Royal Institution on 

 the 7th of June, 1850, and briefly reported in the 'Athenaeum' 

 and ' Literary Gazette ' for the same month, it was shown that 

 when two pieces of ice, at 32° F., with moistened surfaces, were 

 placed in contact, they became cemented together by the freezing 

 of the film of water between them. When the ice was below 32°, 

 and therefore dry, no adhesion took place between the pieces. 

 Mr. Faraday referred, in illustration of this point, to the well- 

 known experiment of making a snowball. In frosty weather the 

 dry particles of ice will scarcely cohere, but when the snow is in 

 a thawing condition, it may be squeezed into a hard compact 

 mass. On one of the warmest days of last July, when the ther- 

 mometer stood at upwards of 80*^ F. in the shade, and above 100^ 

 in the sun, a pile of ice-blocks was observed by one of us in a 

 shoj) window, and he thought it interesting to examine whether 

 the pieces were united at their places of contact. Laying hold 

 of the topmost block, the whole heap, consisting of several large 

 lumps, was lifted bodily out of its vessel. Even at this high 

 temperature the pieces were frozen together at the places of con- 

 tact, though the ice all round these jjlaces had been melted away, 

 leaving the lumps in some cases united by slender cylinders of 

 the substance. A similar experiment may be made in water as 

 hot as the hands can bear ; two pieces of ice will freeze together, 

 and sometimes continue so frozen in the hot water, luitil, as in 



