The Parallel Foods of Glen Boy. 399 



shelves. We see, besides, how the problem is complicated by 

 the additional facts successively brought to light. Had the 

 terraces been found only in Glen Roy, one barrier would have 

 sufficed for the theory, and its existence, though no vestige of 

 it remains, might have been admitted. But the terraces were 

 foimd in Glen Spean, and another barrier must be imagined 

 there against all probability. They were found again in Glen 

 Gloy, differing in level from those of the Roy, and thus a 

 third imaginary barrier is rendered necessary. But the diffi- 

 culties are not yet at an end. Mr Darwin finds terraces at 

 Kilfinnin ; of course a, fourth barrier must be assumed here ; 

 and terraces having been found in the valley of the Spey, a 

 fifth is equally required. Now, it is extremely improbable 

 that even one of these barriers should have disappeared, and 

 left no wreck behind ; but that all the five should have va- 

 nished, and not a vestige of any one of them remain, is utterly 

 inconceivable. 



Mr Darwin attributes the formation of the terraces to the sea, 

 which at an early epoch filled these valleys, as it now fills the 

 cavities forming Loch Eil, Loch Etive, Loch Long, &c. He 

 thinks that the upheaval of the land, followed, of course, by 

 the retreat of the waters, took place slowly and gradually, as 

 in Sweden at this day, not constantly and equably, however, 

 but with intermissions of rest, during which the terraces were 

 formed — that, in fact, these terraces belong to the earlier 

 stages of that great series of movements by which the main- 

 land of Scotland was raised above the water, and of which the 

 last stage is so distinctly marked by the rise of thirty feet in 

 the bed of the Forth. 



As geologists have long been aware that the highest moun- 

 tains have at one time been covered by the sea, this explana- 

 tion must liave occurred to others, who were perhaps led to 

 abandon it by two apparently formidable objections, — first, 

 the entire absence of marine remains from all the terraces ; 

 secondly, their local character, their want of continuity, and 

 their non-exi.stence in hundreds of other locaUties, where they 

 should have been found, on the supi)osition that the cause 

 which produced them was of so general and comprehensive 

 a character. It would be too much to say that Mr Darwin 

 has removed every difficulty which attends his hypothesis, but 



