STRUCTURE OF GLACIER ICE DIRT-BANDS. 245 



usually attract but little attention. Their elope is often very 

 great from 20 to 40. 



Structure of Glacier Ice, and Dirt-Sands. The ice of the 

 glacier proper has a very peculiar structure, quite distinct from 

 the stratification of the snow on the neve (the relics of its mode 

 of deposit), and one which requires special notice. When we 

 examine the appearance of the ice in the wall of an ordinary 

 crevasse (especially if it be tolerably near the side of the glacier) 

 we are struck with the beautiful vertically laminated structure 

 which it commonly presents, resembling delicately- veined mar- 

 ble, in shades varying from bluish-green, through green, to 

 white. It sometimes resembles the marble called in Italy cipol- 

 lino. When we trace the direction of the planes constituting 

 the laminated structure, by observing them on the surface of the 

 glacier (where they are usually well seen after rain, or in the 

 channels of superficial water-runs), we find that where best 

 developed (or not very far from the sides of the glacier) these 

 laminae are nearly parallel to the sides, but rather incline from 

 the shore to the centre of the ice stream as we follow the 

 declivity of the glacier. ' 



The general out-crop of the veined structure may best be 

 seized at a glance by means of a correlative phenomenon thus 

 described by the present writer, who first observed it : " On 

 the evening of the 24th July (1842), the day following my 

 descent from the Col du Geant, I walked up the hill of Charmoz 

 bo a height of 600 or 700 feet above the Montanvert, or 1000 

 feet above the level of the glacier. The tints of sunset were 

 3ast in a glorious manner over the distant mountains, whilst the 

 glacier was thrown into comparative shadow. This condition 

 3f half-illumination is far more proper for distinguishing feeble 

 shades of colour on a very white surface like that of a glacier 

 than the broad day. Accordingly, whilst revolving in my mind, 

 during this evening's stroll, the singular problems of the ice 

 world, my eye was caught by a very peculiar appearance of the 

 surface of the ice, which I was certain that I now saw for the 

 first time. It consisted in a series of nearly hyperbolic brown- 



