Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/401

 part of our island; to pass over the much larger tracts of the globe which must then also have been immersed under it. It is equally apparent, that it must also in this case have had access to innumerable vallies in Scotland precisely similar to Glen Roy in form and composition. Yet in no other instance has a similar series of effects been produced, nor can any other series of analogous phenomena proceeding from such a cause be discovered, to justify the supposition of its having been of a general nature. On the doctrine of chances this hypothesis is attended with the highest degree of improbability, while the locality of the effects strongly bespeaks a local cause, however inadequate may be the explanation already given, and however incumbered with difficulties.

Such are the objections to this hypothesis, of a general nature. The local ones appear no less decisive against it. No marine remains are found in Glen Roy, nor any indications of those deposits of calcareous sand, or of mud containing shells, which ought to be expected at the bottom of a bay where the ocean had rested so long; if even we are not entitled to suppose that solid strata of secondary rocks should have been formed in it. That such substances are found at the bottoms of the present sea lochs of Scotland, is proved by the sounding line; as well as by those banks on their shores which have accumulated by the gradual shoaling of the bottom and exclusion of the sea; and which thus permit the structure of that bottom to be fairly examined. A striking instance in point exists in Isla. In that island a deposit of sea shells is to be found in the neck of land which separates Loch-in-daal from Loch Gruinart; now covered with land alluvia and peat, and evidently a portion of the latter loch shoaled to a small part of its original dimensions. To this local objection I may add another, by barely recalling to the reader's mind that fact respecting the lake of Glen Roy which seems