202 



L. . V. Pirsson —Geology of Bermuda Island ; 



Fig. 2, 



o 



05 



td 



? ^ 



CO z*. -J 



16000 

 FEET 



Argus Bank 



580 Fathoms 

 Challenger Bank 



690 Fathoms 

 100 Fathom Line 



Somerset Id. 

 \ 



Tjt 



i\ 



CD \ 



1 1,500 Feet 

 n_ i above Sea 



Si 



/ Castle Harbor 



100 Fathom Line 



gerated, The writer has redrawn this 

 profile from the Bermuda chart, mak- 

 ing the vertical and horizontal scales 

 the same in order to show the mass in 

 its true proportions. It has also been 

 completed by carrying the slopes 

 down to the ocean floor, for which a 

 mean depth of about 16,000 feet has 

 been assumed. The resultant profile 

 is shown in -Hg. 2. All minor irregu- 

 larities of course disappear when so 

 small a scale is used. It is not pre- 

 tended that this profile has more than 

 approximate accuracy, but it serves its 

 purpose here quite as well in consider- 

 ing the main features of the old vol- 

 cano as a more correct one drawn on a 

 larger scale. In fig. 3 is given a 

 rough sketch map which shows the 

 general form of the volcanic mass. 

 This indicates that on the sea floor the 

 base extends in a northeast and south- 

 west direction some 90 miles as an 

 elongate ridge, whose greatest breadth 

 may be some 25-30 miles. At the 

 sea-level it has been cut away to a 

 platform, which at the 100 fathom 

 line has a length of about 32 miles and 

 a width of 16 miles. Southwest from 

 it are the Argus and Challenger Banks, 

 which are rudely circular in shape, 

 about 5-6 miles in diameter, about the 

 same distance from each other, and 

 about 4 miles from the main platform. 

 From the depth of the valleys which 

 separate them from the main mass and 

 from each other it seems clear that 

 they represent subordinate volcanic 

 cones which have also been cut away 

 by action of the sea. The constructed 

 profile gives for the main outer slopes 

 angles of 12 degrees. The soundings 

 on the Bermuda chart, which give data 

 for the slopes, are as follows, measured 

 in nautical miles (6080 feet) from the 

 100 fathom line in each case : 



