No- Stratification in Drift Materials. 113 



against the rock below in all possible positions ; and hence, 

 not only their rounded form, but also, their rectilinear groov- 

 ing. How such grooves could be produced under the action 

 of currents, I leave to the advocates of such a theory to shew , 

 as soon as they shall be prepared for it. 



I should not omit here to mention a fact which, in my 

 opinion, has a great theoretical importance, namely, that in 

 the northern erratics, even the largest boulders, as far as I 

 know, are rounded, and scratched and polished ; at least, all 

 those which are found beyond the immediate vicinity of the 

 higher mountain ranges, shewing that the accumulations of 

 ice which moved the northern erratics covered the whole 

 country ; and this view is sustained by another set of facts 

 equally important, namely, that the highest ridges, the highest 

 rugged mountains, at least, in this continent and north of the 

 Alps in Europe, are as completely polished and smoothed as 

 the lower lands, and only a very few peaks seem to have 

 risen above the sheet of ice ; whilst, in the Alps, the summits 

 of the mountains stand generally above these accumulations 

 of ice, and have supplied the surface of the glaciers with 

 large numbers of angular boulders, which have been carried 

 upon the back of glaciers to the lower valleys and adjacent 

 plains without losing their angular forms. 



With respect to the irregular accumulation of drift-mate- 

 rials in the north, I may add, that there is not only no indi- 

 cation of stratification among them, such, unquestionably, as 

 water would have left, but that the very nature of these 

 materials shews plainly that they are of terrestrial origin ; 

 for the mud which sticks between them adheres to all the 

 little roughnesses of the pebbles, fills them out, and has the 

 peculiar adhesive character of the mud ground under the 

 glaciers, and diff'ering entirely in that respect from the 

 gravels, and pebbles, and sands washed by water-currents, 

 which leave each pebble clean, and never form adhering 

 masses, unless penetrated by an infiltration of limestone. 



Another important fact respecting this glacial draft con- 

 sists in the universal absence of marine, as well as fresh- 

 water fossils in its interior— a fact which strengthens the- 



VOL. XLIX. NO. XCVII. — JULY 1850. H 



