ii6 Mr. H. H. Howorth on 



upwards and outwards where the ice is supported by the 

 lateral rocks. When the glacier acquires a rounded or oval 

 contour, the lines become more or less oval in curve, and 

 dip inwards at angles more nearly perpendicular as the 

 centre of the glacier is approached, and may be compared 

 to sections of inverted cones, having a common apex 

 pointed downwards with its angles continually diminished 

 towards the centre {Travels in the Alps of Savoy ^ 29, 160,. 

 372, etc.). 



The course of the bands being vertical they crop out at 

 the surface, and wherever that surface is intersected and 

 smoothed by superficial watercourses, their structure appears 

 "with the beauty and sharpness of a delicately-lined chalce- 

 dony." This structure Forbes proved pervaded the whole 

 body of the glacier, and wherever a vertical section was eroded 

 by the action of water, the harder seams of ice stood pro- 

 tuberant, while the immediate ones, partaking of a whitish 

 green in colour, were washed out. He subsequently found 

 that the blue bands are due to compact ice, and the inter- 

 mediate ones to the ice being frothy and full of bubbles. The 

 structure was apparent throughout the length of the glacier,. 

 but was more developed in the neighbourhood of moraines 

 and the walls of the glacier. That it was not the product 

 of a single season, Forbes showed by tracing the bands 

 across the gaping glaciers. Throughout the greater part of 

 the glacier the bands are parallel to the enclosing walls, 

 but near the lower extremity they change their direction 

 and become transverse, and lean forward in the direction 

 in which the glacier moves at a very considerable angle. 

 Forbes argued that " the veined or ribboned structure 

 of the ice is the result of internal forces, by which 

 one portion of ice is dragged past another in a manner 

 so gradual as not necessarily to produce large fissures 

 in the ice, and the consequent sliding of one detached 

 portion on another, but rather the effect of a general 



