XXXU PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



tion over the north-eastern part of the North American continent, 

 and that the erratic blocks and other transported matter have come 

 in the same direction. In northern Europe, v/hen the striating agents 

 had quitted the Scandinavian mountains, they met with no other 

 mountains of sufficient magnitude to impede their general course, or 

 materially modify the directions of movement ; but in America the 

 striation, according to the American geologists, has been carried 

 not only transversely but obliquely over some of their highest moun- 

 tains, without material deviation from its normal direction, except 

 along or near the bottoms of some of the valleys, in which cases the 

 direction of the striae nearly coincides with those of the valleys. 



This coincidence of direction in the lower parts of the valleys is 

 exactly what we should expect, and is accordant with the character 

 of the like phsenomena in Europe ; and the persistency of transverse 

 oblique directions in the striae over the upper parts of elevated tracts 

 presents no difficulty ; for so long as the striating agent (as an ice- 

 berg) should only come in contact with those upper parts, its opera- 

 tions could not be influenced by the depths of the valleys below. But 

 what takes place at intermediate heights between the bottoms of the 

 valleys and the tops of the mountains ? It is impossible to suppose, 

 if the side of a mountain were striated in every part, that while the 

 striae at the bottom should be parallel to the lateral valley or axis of 

 the mountain, and those at the top should be, for instance, perpen- 

 dicular to it, the striae at intermediate heights should not have some 

 intermediate directions in passing from one extreme limit to the other. 

 Careful observations ought to be made on this point. The height to 

 which the striae preserve their parallelism with the valleys below, and 

 the distance from the tops of the higher ridges across which they pre- 

 serve their transverse directions, should be most carefully noted. Nor 

 ought any geologist, in a delicate question of this kind, to trust to 

 vague measurements and general impressions. Every direction ought 

 to be carefully taken and as carefully laid down on a good physical 

 map, together with the dip and strike of the striated surface. The 

 general configuration, too, of the imm.ediate vicinity should be de- 

 scribed, with reference to its probable influence on the motion of any 

 mass to which the striae may be attributable. Again, it has been 

 said that in many cases the lee side and storm side of an elevated 

 ridge are sometimes equally marked by striae transverse to its direc- 

 tion. This seems entirely at variance with our observations on this 

 side of the Atlantic, except in those cases in which the striae are 

 attributable to local action, in contradistinction to that more general 

 action of such agents as masses of ice, for instance, driven in one di- 

 rection over the whole region from^N.W. to S.E. I have not 

 hitherto been able to represent to myself the physical possibility of 

 striae on the lee side remote from the top of the ridge, having been 

 produced by the general action just referred to. May they not have 

 been more frequently due to local action than has been suspected 1 

 The glacial theories, on their first introduction, did not, I think, 

 make so much impression on the minds of American as on those of 

 European geologists, and many of the recorded observations of striated 



