Dana and Chambers on Ancient Sea-Margins. 213 



on both sides of Glen Roy, and look like " copy lines ruled for 

 text." The first and second, or two upper, were found by 

 MacCullocli to be 82 feet apart, and the second and third 212 

 feeti A careful survey by Mr David Stevenson, according to 

 Mr Chambers, made the latter 212-37 feet, and the former 

 80*32 feet, a close approximation to MacCuUoch's determina- 

 tion. The height of the uppermost, above high tide, is 1139 

 feet; of the second, 1059 feet; of the third, 847 feet.* 



Adjoining Glen Roy lies Glen-Gluoy, which opens below 

 upon Loch Lochy. This valley has two distinct shelves or 

 terraces, one 1159 feet above high tide, and the other 959 to 

 969 feet. Other shelves occur in Glen Spean, as well as in 

 Glen Roy, whose heights are mentioned in the table on page 

 210. The whole system has afforded a fruitful and most in- 

 teresting subject of speculation. The " perfect horizontality" 

 of the terraces (their height above the present bottom of the 

 valley therefore diminishing upwards, instead of rising with 

 the valley), their extent, and the character of the region 

 around, are the bases of the two views recently urged, the 

 one attributing them to inland lakes, the other regarding them 

 as beaches of an arm of the sea. 



Mr Chambers adopts the latter view ; and as he discusses 

 the character of the other terraces of Scotland and England, 

 he arrives at the same conclusion for them all. He finds the 

 same " ancient sea margins" in foreign regions. In France 

 and North America he seems to detect terraces of equivalent 

 height with those of Scotland, and all are set down as mark- 

 ing former levels of the sea. A natural terrace and a sea- 

 beach are therefore, in his view, nearly synonymous terms. 



We do not pretend to deny, without examination, the con- 

 clusion, in particular cases, carefully studied by Mr Chambers. 

 But the sweeping deduction needs much, very much restriction. 

 And even many of his own examples demand better proof of 

 the former presence of the sea than has been presented. 



The principle that " what has been, may again be, and the 

 reverse," is acknowledged to be a safe test of truth in geology. 



* MacCuUoch observes, that the first is 927 feet above the level of the junc- 

 tion of the Roy and Spean. 



VOL. XLVI. NO. XCII. — APRIL 1849. P 



