262 MR. T. CODRIi;rGTON ON SUBMEEGED EOCK-VALLETS [Aug. 1 898, 



II. Devon and Coenwall. 

 The Dart. 



The lower course of the river Dart lies between steep banks of 

 Devonian slate. Its eptrance from the sea is but 250 yards wide, 

 inside which is Dartmouth Harbour, into which several creeks open 

 Two miles up the river is another narrow part, which is crossed 

 by two greenstone-dykes. Above that is a remarkable lake-like 

 expanse of water more than a mile wide, and reaching to within 

 I5 mile of Torbay. 



Across the narrow part of the river, below this, near Maypool, 

 borings were made for a proposed bridge. There is 43 feet of 

 water at low-water spring-tides at the deepest place where the 

 section (fig. 8) was taken, and 43 feet of mud and silt was found 



X. 



Fig. 8. 



Rmer Dar.t 



Section acfoss r.iuer 



at Ma nDool 



Scales 

 Worizontal::400 feet=1 inc/i] 

 IVertisal:^ 1.00 feet^l inchj 



below that. The greatest depth to the rock-bottom reached was 110 

 feet below the level of low water spring-tides, under 85 feet of mud 

 and silt. The average slope of the rock-sides, as shown in the section, 

 is 1 in 3| on the south side, and 1 in 3 on the north side, corre- 

 sponding with the slopes above the water-level, which rise to 130 and 

 150 feet above the river. The real slopes are steeper, as the section 

 crosses the river obliquely ; for the same reason, a section at right 

 angles to the valley would be narrower. Dark red clay and fine 

 shillet (Devonian shale) are recorded as overlying the rock on the 

 southern slope. 



About I mile below this section, on the left bank of the river, 

 Longwood Creek is crossed by the railway. The piles of the 



