40 THE SUB-GLACIAL STREAM. 



gether. 1 Supposing that the deposit only reaches 3 inches in the 

 year, there is a bank or flat 25 feet thick formed in the course of a 

 century. However, any one who has seen these muddy sub-glacier 

 streams, and the way in which they deposit their mud, must be 

 convinced that this estimate is far below the mark, and that an 

 important geological deposit, which has never been rightly ac- 

 counted for (if even noticed, as far as my observation goes), is form- 

 ing off the coast of Greenland and wherever its great glaciers pro- 

 trude into the deep quiet fjords. It ought also to be noticed that the 

 fjords which have been the scenes of old ice-streams, in almost every 

 instance end in a valley at the head, this valley being due, first, to 

 the glacier which reclined on it and hollowed it out and, secondly, and 

 further down, to the filling up of it by the glacier-ulay. This form 

 of fjord is not only common in Greenland, but also in every other 

 part of the world where I have studied their form and formation. 



After carefully examining and studying this clay, I can find no 

 appreciable difference between, it and the brick-clay, or fossiliferous 

 Boulder-clay. Mr. Milne Home, 2 among other arguments against 

 the theory that Boulder-clay has been formed by land-ice, remarks 

 that he saw nothing forming in Switzerland at all comparable to 

 Boulder-clay. Reserving to ourselves a doubt on that subject, lean 

 only say that long after my opinion regarding the identical cha- 

 racter of the subglacial-stream-clay and the fossiliferous brick-clay 

 was formed, a very illustrious Scandinavian Arctic explorer visited 

 Edinburgh and declared, as soon as he saw the sections of Boulder- 

 clay exhibited near that city, that this was the very substance 

 he saw forming in under the Spitzbergen ice. Many theoretical 

 writers, however, confound the ordinary non-stratified azoic clay, 

 and the finer, stratified fossiliferous clay. 



In this clayey bed the Arctic Mollusca and other marine animals 

 find a congenial home, and burrow into it in great numbers. How- 

 ever, as new deposits are thrown down, they keep near the surface, 

 to be able to get their food ; so that if to-day a catastrophe were 

 to overwhelm the whole marine life of the Arctic regions, it would 

 be found (supposing by upheaval or otherwise we were able to 

 verify the fact) that the animals would only be imbedded in the 

 upper strata of clay, and that the bottom one, with the exception 

 of a few dead shells, would be azoic ; yet I need not say how erro- 

 neously we should argue if, from this, we drew the inference that, 



1 I am glad to find that, independently, this identical view is held by Mr. 

 J. W. Tayler, who resided for several years in Greenland, ' Proc. Roy. Geogr. 

 Soc.,' v. p. 90 (1861). 



- ' Trans. Roy. Soc. Edin.,' vol. xxv. p. 661 ; and ' Estuary of the Forth ' (1S71). 



