174 ON THE REVOLUTIONS 



ness. This mass shews itself in several places, in the bed of 

 the water of Leith, where the banks have been laid open by 

 natural or artificial means. It was well displayed formerly, 

 and may still be seen above the Bells' Mills Quarry, and is 

 now exposed to view upon the right hand, after crossing the 

 Dean Bridge, on the old road to Queensferry. It here pre- 

 sents to view a face of about twenty or thirty feet deep, though 

 it often extends to forty or fifty feet. We find it also upon the 

 shore to the west of Leith, as laid open by the sea ; and I am 

 informed by the person who conducted the work, that at the 

 Fort in that neighbourhood, in a search for water, it has been 

 penetrated to the depth of eighty feet from the surface, being 

 fifty below high-water mark. It is obvious, that the power of 

 such mud, when flowing as a stream, in transporting heavy 

 bodies, and in abrading assemblages previously formed, must 

 bear some relation to the resistance which it would oppose to 

 any object forced through it, and of course, that its power in 

 these respects must have been much superior to that of pure 

 water. I conceive also, that a deep stream must exert a great- 

 er power of transportation and corrosion than one which is 

 shallow, flowing with the same velocity. 



The existence of assemblages of this sort, affords, by its 

 simple testimony, a powerful argument in favour of a stream 

 having overflowed this country, superior in magnitude to any 

 known river ; and the facts seem to meet the challenge held 

 out by Mr Playfair in the following passage, Illustrations^ 

 art. 366. " Lastly," he says, " if there were anywhere a hill, 

 " or any large mass composed of broken and shapeless stones, 

 " thrown together like rubbish, and neither worked into gra- 

 " vel, nor disposed with any regularity, we must ascribe it to 

 " some other cause than the ordinary detritus and wasting of 

 ■** the land. This, however, has never yet occurred, and it 





" seems 



