] 857.] Observations on Glaciers. 321 



contortions of the ice, the quicker movement of the centre where 

 the ice is uninfluenced by the retardation of the banks, are all cir- 

 cumstances which have been urged with such constancy and ability, 

 as to leave the viscous theory without any formidable competitor at 

 present. To these may also be added, the support which the theory 

 derived from its apparent competency to explain the laminar struc- 

 ture of the ice — a structure regarded by eminent authorities as a 

 crucial test in favour of the viscous theory, and which was affirmed 

 to be impossible of explanation on any other hypothesis. 



Nevertheless, this theory is so directly opposed to our ordinary 

 experience of the nature of ice, as to leave a lingering doubt of its 

 truth upon the mind. To remove this doubt, it is urged, that the 

 true nature of ice is to be inferred from experiments upon large 

 masses, and that such experiments place the viscosity of ice in the 

 position of a fact, rather than in that oj a theory. It has never 

 been imagined that the bendings and contortions, and other 

 evidences of apparent viscosity exhibited by glaciers, could be made 

 manifest on hand specimens of ice. But this was shown by 

 the speaker to be experimentally possible. Moulds of various 

 forms were hollowed out in boxwood, and pieces of ice were placed 

 in these moulds and subjected to pressure. In this way spheres of 

 ice were flattened into cakes, and cakes formed into transparent 

 lenses. A straight bar of ice, six inches long, was passed through 

 a series of moulds augmenting in curvature, and was finally 

 placed before the audience, bent into a semi-ring. A small block 

 of ice was placed in a hemispherical cavity, and was pressed upon 

 by a hemispherical protuberance not large enough to fill the cavity ; 

 the ice yielded and filled the space between both, thus forming 

 itself into a transparent cup. In short, it was shown that every 

 observation made upon glaciers, and adduced by writers on the 

 subject in proof of the viscosity of ice, is capable of perfect imita- 

 tion with hand specimens of the substance. 



These experiments then demonstrate a capacity on the part of 

 small masses of ice, which has hitherto been denied to them. They 

 prove, to all appearance, that the substance is even much more 

 plastic than it was ever imagined to be by the founders of the 

 viscous theory. But the real germ from which these results have 

 sprung, was to be found in a lecture given at the Royal Institution, 

 in June 1850, and reported in the AthencBum and Literary Gazette 

 for that year. Mr. Faraday then showed, that when two pieces of 

 ice, at a temperature of 32** Fahr., are placed in contact with each 

 other, they freeze together, by the conversion of the film of moisture 

 between them into ice. The case of a snowball was referred to as 

 a familiar illustration of the principle. When the snow is below 

 32", and therefore dry, it will not cohere, whereas, when it is in 

 a thawing condition, it can be squeezed into a hard mass. During 

 one of the hottest days of last July, when the thermometer was 

 upwards of 100" Fahr. in the sun, and more than 80° in the shade. 



