76 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



that time, after the manner of granite just intruded. The Lower 

 Carboniferous rocks afterwards deposited among the Devonian ridges 

 in the east were, in their turn, folded, and they too compose a sub- 

 ordinate part of the plateau. 



form. — But all this constructional topography due to folding has 

 been changed (Plates 1 and 2). The geologist now directs his exploring 

 canoe over a thousand square miles of granite moulded in the low re- 

 lief of gently undulating hills separated by shallow lakes. He finds but 

 little trace of the mountain-cover which blanketed the intrusions and 

 permitted the slow crystallization of the vast igneous bodies. As little 

 does he anywhere Hud the original surface of the ranges. There remain 

 to him only the edges of slate or quartzite band, that once, to right, 

 stretched up over the roof of a now vanished arch, and, to left, formed 

 half of a ruined trough, which he can still decipher, though tattered 

 and corrugated on its rims, the roots of an all but completely destroyed 

 mountain mass. Throughout these fifteen thousand square miles, the 

 observer finds no hill more than one thousand feet high, and ninety 

 per cent of the plateau is less than six hundred feet in altitude above 

 the sea. It will be well to note some of the readings of elevation which 

 I have compiled from the various sources already mentioned ; many of 

 them are merely barometric determinations, but no serious error is 

 believed to result from their use. 



In addition to the fact that the coastal elevations are low, it was 

 speedily observed that they are systematically related. At the mouth of 

 St. Mary's Bay, the bed-rock surface of the hill-tops stands at from one 

 hundred and fifty to two hundred feet above the sea. Thence a more 

 rapid rise northeastwardly brings the average summit southeast of Digby 

 to the five-hundred-foot contour, and the long escarpment of " South 

 Mountain," running north-east by east, remains at that elevation for 

 some sixty-five miles. Along the roughly parallel line of the Atlantic 

 coast, the heights vary from seventy feet at Cape Sable to one hundred 

 and fifty feet at Halifax. Profile sections taken transverse to these two 

 belts of elevation show that there is a fairly gradual descent from one 

 to the other, in a southeast by south direction, a descent interrupted 

 only by local and faint reliefs to which reference will presently be made. 

 It will be further noticed that the greater height of the hills near Hali- 

 fax is related to a corresponding proximity of the Atlantic shore to 

 "South Mountain," proving an essentially equivalent angle of slope for 

 the surface throughout the western half of the plateau as far as the 

 town of Digby. The same angle and direction of slope characterizes 



