264 APPENDIX, NO. I. 



I think, have a real existence. It is a result to which the dirt-bands 

 may be the indication, or it may have passed altogether unobserved. 



" We find at the heads of most glaciers, where the neve is passing 

 into ice, and the body assuming its normal form and construction, that 

 there are steeper elevations, from which the neve descends, and fre- 

 quently ice-cascades. The glacier is in these parts, on account of 

 the abrupt descent, very much broken up, and often impassable. 

 Now it appears evident, that, at the foot of these slopes, the water 

 which has passed more quickly down them will accumulate to a greater 

 extent than if there had been no elevation behind, on account of the 

 change of inclination. Now, during the summer months, the satura- 

 tion thus taking place will be greatest, because of the large quantity 

 of water then coming down. At this period of the year, likewise, the 

 motion of the glacier is also greatest, and a large advance of the satu- 

 rated body occurs. This, during the winter frosts, is consolidated, 

 and formed, I imagine, into more compact ice than would have resulted 

 from less saturated material. 



" On the other hand, in the winter months, that part of the glacier 

 at the foot of the upper slopes, or ice-cascades, will be less saturated, 

 as the surface of the whole glacier is then in a state of comparative 

 rest, in consequence of the diminished effect of the sun's rays in thawing 

 the surface of the neve. At this time, also, the glacier moves with 

 far less rapidity ; and so the quantity of glacier in a less saturated 

 state thus moving on, will be considerably less than that advancing 

 during the summer. In consequence, also, of its being Jess saturated 

 with water, it will, after consolidation, be less compact than that which 

 moved forward during the summer. Viewed in this light, the foot of 

 the upper slopes, or ice-cascades, may be considered as a kind of 

 laboratory for the manufacture of alternate bands of compact and porous 

 i ce the former made during the summer, and the latter in the winter 

 months. Thus, if my theory be correct, a wide band of comparatively 

 compact ice, and a narrow band of porous ice, will be annually formed 

 and added to the glacier. 



" If these alternate bands be considered as identical with the porous 

 and compact bands to which the dirt-bands belong, it follows, that the 

 porous bands, during the progress down the glacier, become apparent 

 by the absorption of the drift, which is washed over the surface, and 

 their distinctness increases with the length of time during which they 

 have been subjected to the drift. 



" Thus the wide compact band answers to the interval between the 



