6 STRUCTURE OBSERVED IN THE ICE OF GLACIERS. [1841. 



obscured. There seems no doubt, however, that the horizontal 

 stratification in the lower part of glaciers, insisted on by several 

 writers, is merely a deception arising from this cause, so familiar 

 to the geologist who gets a section perpendicular to the dip of 

 strata, which, therefore, appear horizontal. Towards the sides 

 or walls of the glacier, at its lower extremity, the veins have 

 their plane twisted round a vertical axis, having now their dip 

 towards the centre of the glacier, and rising against the walls ; 

 and this inclination sometimes extends nearly to the axis of the 

 glacier, or the medial moraine, where I have observed the veins 

 deviating from the vertical by an angle of about twenty degrees, 

 the bands inclining from the centre (or rising towards the 

 walls), as if the pressure arising from the superior elevation ol 

 the glacier under the moraine had squeezed them out. The 

 whole phenomenon has a good deal the air of being a structure 

 induced perpendicularly to the lines of greatest pressure, though 

 I do not assert that the statement is general. Whilst the 

 glacier is confined between precipitous barriers with a feeble 

 inclination, the structure is longitudinal. As the glacier, by 

 its weight, falls over the lower part of its bed, and moulds itself 

 into the form which the continued action of gravity on its 

 somewhat plastic structure impresses, the longitudinal structure 

 is first annihilated (for throughout a certain space we could 

 detect no indications of one kind or other), and the bands then 

 reappear in a transverse direction, as if generated by the down- 

 ward and forward pressure, which, at the lowest part of the 

 glacier, replaces the tight wedging which higher up it received 

 laterally. It is not easy to convey without a model a clear 

 idea of the forms of surface here intended, and which yet re- 

 quire considerable correction. 



I may mention, however, that the glacier of the Rhone, 

 which I have carefully examined, presents a structure in con- 

 formity with the view thus developed. It will be recollected 

 by all who have seen that magnificent mass, that it pours in 

 colossal fragments over the rocky barrier which separates the 

 Gallenstock from the valley of the Rhone, and having reached 



