Dr. Mac Culloch on the Parallel Roads of Glen Roy. 391 



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 innu- 

 merable 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 phe- 

 nomena 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 sub- 

 stances 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 



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