296 In and Around the Morteralsch Glacier: 



travel the glacier so easily. Were it possible, after the removal 

 of the white outer layer and exposure of the blue ice, to 

 submit this to the action of heat of convection alone, the ice 

 would melt with a smooth surface, as can be observed on the 

 inner walls of the grotto in summer. A glacier having such 

 a surface would be barely passable. After the individual 

 grains have been thus laid bare they themselves experience 

 a further disintegrating effect under the continued action of 

 the sun's rays, which is the same in kind as that produced on 

 massive glacier-ice. As the sun's rays analyse a piece of 

 glacier-ice, separating its constituent grains, so they continue 

 the analytical process on the isolated grain or crystal, and 

 separate it into its constituent lamellae, which are situated 

 normally to the principal axis of the crystal. Both of these 

 analytical separations are due to the power of the sun's rays 

 to detect the impurities which occur even in the purest crystal, 

 and to eliminate them by discriminating fusion. 



Having found that the whiteness of the ice on the surface 

 of the glacier is a secondary feature and is due to its exposure 

 to solar radiation, the question naturally arises, does white ice 

 occur in the interior of the glacier? In order to answer this 

 question it is necessary to be able to penetrate into the 

 interior of the glacier. 



The Morteratsch Grotto. 



As has been already indicated, the most convenient place 

 to study such a subject is the interior of the artificial grotto, 

 which is to be met with in all frequented glaciers. 



The Morteratsch glacier is one of these ; and at the date 

 of my first visit, in the summer of 1893, there was a very fine 

 grotto, driven in the western flank of the tongue of the glacier, 

 which at that date extended more than a hundred metres 

 further down the valley than it does now. I visited it almost 

 daily, and at each visit I had the opportunity of observing 

 phenomena which I did not expect. In the following February 

 (1894) I returned to the Engadine in order for the first time 

 to see a glacier and an ice-grotto in winter ; the phenomena 



