H2 



The Glacial Theory, 



and in Scotland ; but there is this distinction to be made, that these 

 blocks are generally not far distant from their natural position in situ, 

 or that they are in small number compared with those which have 

 evidently been acted on by a prolonged mechanical operation. But 

 this is not all: far from being found lying at the surface of the 

 ground, the large blocks are for the most part heaped up in a 

 confused manner along with the smaller ones of all degrees of size, 

 from the dimensions of the smallest pebbles to the colossal volume 

 of the largest erratic blocks, in a deposit of clay unequally distributed 

 over all the low portions of the country. This deposit of clay, which 

 is of very unequal thickness, and exhibits no trace of stratification, is 

 what is termed till in Scotland. There is no locality in which I have 

 been able to study the till more completely than at Glasgow, where 

 the numerous works carried on in 1840, for the embellishment of the 

 town had exposed it at many points; but everywhere it presents the 

 same character ; the rounded, polished, and scratched blocks of very 

 various dimensions, are every where indiscriminately mixed together 

 in a marly or clayey paste. It is evident that it was with this mass, 

 and in this mass, that the rounded and polished blocks have been trans- 

 ported during the whole journey which they have performed together, 

 while the angular blocks have certainly not been rubbed in this man- 

 ner. Mr. T. Edington has, to the advantage of geologists, brought 

 together, in his park at Glasgow, a magnificent collection of these 

 polished and scratched blocks from the neighbourhood of the town. 



Differences of this description in the facts observed at different lo- 

 calities, are an additional difficulty for all those who endeavour to 

 explain them by means of currents. How, indeed, can it be now 

 seriously pretended that a current can convey blocks in such a man- 

 ner as to rub, round, and scratch one set of them, without then* being 

 heaped up according to their weight, and without their being cover- 

 ed by regular beds of finer materials, while the others remained an- 

 gular, and retained their unequal and rough surfaces ? These differ- 

 ences are very favourable to the glacier theory, which explains them 

 in a manner that is quite natural. 



Let us return to the glaciers of the present day, and we shall find 

 in some of the phenomena presented by them the greatest analogy 

 to the arrangement of erratic blocks, as I have just described it. 



