A Study in the Natural History of Ice 307 



of a part of the ice possessing a smooth surface and perfect 

 transparency, properties which it was able to preserve in spite 

 of the apparently perfect freedom with which the sun's light 

 penetrates the water and renders visible to the eye the sub- 

 merged features of the berg. From this it follows necessarily 

 that the particular rays which bring about the disintegration 

 of the glacier-ice are absorbed by water, while, on the other 

 hand, they are transmitted abundantly by ice. 



Even the largest berg in the Mergelin See is a very small 

 object compared with the blue berg seen in the Antarctic, and 

 with its insignificant mass the proper colour of its ice is much 

 attenuated ; it is represented by a delicate bluish tint. 



We see then that equal protection is afforded to the ice from 

 the disintegrating rays of the sun by the fresh water of an 

 Alpine lake and by the salt water of the ocean. Naturally the 

 water can afford this protection to the ice only by absorbing these 

 rays itself, and in doing so it must be warmed correspondingly. 



Hugi's Fundamental Experiments. 



We now have the information which enables us to follow 

 in detail and to explain the capital experiment first made by 

 Hugi in the year 1822. 



When a piece of fresh glacier-ice is fetched from the 

 Antrum or the grotto, or from some place inside the glacier 

 where the ice is protected from radiation from the sky, and is 

 then exposed to the rays of a powerful sun, in a very short 

 time it crumbles together and falls into a heap of individual 

 glacier-grains. 



We have seen that the ice in the interior of the glacier is 

 always at the melting-point of the ice on the intergranular 

 surfaces, which is influenced by the relative purity or impurity 

 of the water occupying the intergranular spaces. As the 

 purity of the ice-crystal which remains solid is always greater 

 than that of the water in contact with it, the mass of the grain 

 is protected by the lower temperature at which its superficial 

 layers melt. But no matter what the melting temperature 



