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 order 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 relief 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 Upitanp Penepiain. — 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 
