76 ROYAL SOCIETY OF CANADA 



which lies west of Halifax Harbour and extends southward in Sambro 

 ledges. Its crest comes within 47 fms. of the surface while about it is 

 water exceeding 100 fms. in depth except to the north where it is 

 separated from Sambro ledges merely by a narrow channel. 



On its east side close to its base there is a depth of 153 fms. and 

 the isobathic lines parallel its length with here and there a crest break- 

 ing an absolute uniformity. 



Soundings exceeding 140 fms. extend for 40 miles giving direction 

 of deepest water towards the north-easf, with remains of lateral 

 branches ; while in the other direction towards the open ocean the bottom 

 r^'ees to 90 fms. and unless there be a narrow deep channel which as yet 

 has not been recorded, the course of the ancient drainage) is so dammed 

 up that an elevation of GOO feet would make a large lake with Sambro 

 bank as an island in the middle. The ' Owl ' and other two small 

 banks would make peaks above the surface of the lake. The structure 

 of this valley suggests that the rocks here are slate and quartzite with 

 foldings such as tlie operations of the gold miner have shown to be so 

 regular on the land and made familiar to everyone. West of Sambro 

 bank there is also water exceeding 130 fms. in depth, but the soundings 

 indicate no such structure as that to the east of the bank and about 

 Sable Island. Doubtless this condition of the seabottom may be ac- 

 counted for by the strong flow of the currents of both water and Ice 

 under the influence of the great tide of the Bay of Fundy obscuring 

 the older features. 



That the Sambro valley was one of river erosion although its outlet 

 is now closed, there can be, I think, but little doubt. The recent eleva- 

 tion and subœrial erosion of lands both east and west must have affected 

 thia region also, and explanation must elsewhere be sought to account for 

 the mass of deposits that have closed the sometime outlet seaward of 

 Sambro bank. The charts note several of the shallow soundings on 

 the shelf as ' rocky,' these all lie within 40 miles of the coast, and 

 many of the deeper depressions are marked as having a mud bottom. 

 The inference from the exposure of the rocky peaks is that they were 

 passed over by the deposit flowing from the land. The presence of 

 mud in the deeper parts that there was there no indiscriminate dumping 

 of moraine matter from ice, but the slow accumulation of fine sediment 

 in quiet waters. 



It is plain, however, that the preglacial features of the region can 

 be surmised only in part, as they have been more or less covered over 

 and disguised by later sediments. The bulk of these sediments appears 

 to iiave accumulated towards the front of the plateau having here and 

 there deep depressions between them and the shore. Ranging with the 



