MR MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 479 



stones and basalts in the second. Moreover, whilst, during the former period of 

 eruption, the lines of fracture were invariably east and west, on this last occasion 

 they were west-north-west and east-south-east. Nor is this last direction merely 

 that of the trap dykes ; for it has been seen that there is one set of fissures or 

 joints in the rocks themselves, and which pervade all the strata, from the oldest 

 to the newest, running in much the same direction. If any explanation of these 

 combined and complex phenomena is to be sought, on the hypothesis before re- 

 ferred to, we may suppose that the shape of the earth's nucleus changed, so as to 

 become, immediately below this part of its surface, more convex than before, and 

 to form a sort of ridge running in a west-north-west direction. The pressure of 

 this bone of the nucleus on the outer skin, would have a tendency to produce frac- 

 tures or cracks immediately above it, and in lines parallel with itself; whilst 

 through these cracks molten matter would gush out, and form both dykes and 

 coulees. At the same time, so much heat would be communicated to the whole 

 of the rocks, both stratified and unstratified, composing the earth's crust, that 

 chemical affinities would be called into action, the matter of these rocks would 

 begin to re-arrange itself, and thus multitudes of minor cracks in these rocks 

 would be produced, which would approximate to a west-north-west direction, that 

 being, in the circumstances above described, the line of greatest weakness. 



5. The next important epoch, in the history of those convulsions to which 

 this district, in common with the rest of the island, was subject, is connected with 

 the formation or deposition of the clay, gravels, sands, and boulders which cover 

 the rocks. To this class of phenomena much interest attaches, not merely from 

 the general and abstract difficulty of explaining them, but also from the attempt 

 which has recently been made, supported by great zeal and talent, to account for 

 them all by glacial action. 



Now, I freely admit that the problem is exceedingly complex, and that, there- 

 fore, every attempt to solve it should receive due consideration. Nor do I pre- 

 tend to say, that any explanation of all the phenomena presents itself, which is 

 quite satisfactory even to my own mind. But, whatever the true theory may be, of 

 one thing I am satisfied, that glaciers could not have transported the boulders, or 

 produced the remarkable accumulations of gravel and sand which occur in this 

 part of Scotland. 



(1.) What cause can be suggested for the transportation of the numerous 

 boulders strewed over Roxburghshire, and especially the blocks of granite which 

 occur in Liddesdale ? 



In the previous part of this Memoir, when noticing the situation of the boul- 

 ders, to whatever species of rock they belong, I shewed that the parent rocks 

 were, in all cases, to the westward of the boulders. 



In some of these cases, the situation and relative levels of the parent rocks 

 and the boulders are such, that there is, on that account, no impossibility in sup- 



