DALY : PHYSIOGRAPHY OF ACADIA. 87 



of the lowland belts probably extended along their planes of stratification 

 to altitudes higher than the existing summit-line of North Mountain. 

 The traps must certainly have stretched upward for some distance be- 

 yond the same line. One evidence for this is found in the independence 

 of the longitudinal ridge-profile and the dip of the trap ; at Blomidon it 

 measures 15°, at Digby Gut, 5° to 10°; near Bridgetown the beds lie 

 horizontal (Bailey, '98, p. 128). Yet we have seen that the upland level 

 remains very constant at about 550 feet throughout the whole distance 

 including these three points. The truncation of the constructional ridge 

 is even more clearly shown in the transverse profiles. A good example 

 appears in the extended view which one gets toward the southwest from 

 " Look-off," near Canning (Plate 8). There the upland surface is flat 

 and nearly level, without a decided slope to the north until the Fundy 

 sea-cliff is reached, while the dip is about 15° to the north. It is the 

 perfect level-topped sky-line of a typical plateau, not that of the back- 

 slope of a tilted lava-block. Such a sky-line would be extremely diffi- 

 cult to explain as belonging simply to the retreating escarpment of a 

 trap sheet, wasting during the first cycle following uplift. Nor could 

 the doctrine of " beveling " be applied here with any success ; more 

 probable would be the hypothesis of marine erosion. 



The key to the problem is to be found in the sympathetic relationship 

 already described between the upland facet of the Southern Plateau and 

 this other one of North Mountain. The latter is a residual of the grand 

 peneplain which we have traced from Cape Sable to the Cobequids, the 

 New Brunswick Highlands, and beyond. The peneplain was tilted, its 

 streams invigorated, and thereby narrow valleys were cut in the harder 

 pre-Carboniferous rocks, and the lowland from Truro to the mouth of St. 

 Mary's Bay on the soft Triassic sandstones. In oi'der to understand 

 this and the adjoining lowlands of Acadia, it will be well to determine 

 as nearly as may be, and more in detail than heretofore, the amount and 

 directions of tilting which the peneplain has suffered, and thus get some 

 idea of the constructional l'elief at the beginning of the second cycle. In 

 thus treating of the deformations of a baselevelled land-surface, it is real- 

 ized that we are taking another step in the direction of pure theory ; but, 

 if the peneplain explanation be regarded as correct, the step is necessary. 



"Warping of the Upland Peneplain. — As suggested on an earlier 

 page, the most significant displacement of the peneplain from its original 

 position near sea-level consisted in a tilt directed about S. 30° E., affect- 

 ing nearly uniformly all parts of the facet east of a line passing through 

 St. John and Digby. This differential movement must have been greater 



VOL. XXXVIII. — no. 3 2 



