

the Igneous Platform. 





2( 



S.S.W. 



Argus Bank 



8 miles 



1870 fathoms 



= 12° 



S.E. 



a 



a 



13 " 



2250 



a 



= 9° 



N.W. 



Challenger 



tt 



5-5 " 



2175 



a 



= 23° 



S.E. 



a 



a 



11 



1820 



a 



= 10° 



S.E. 



Main 



a 



" 



1240 



it 



= 11° 



N.E. 



a 



a 



6 



1260 



a 



= 12° 



N.W. 



a 



a 



4 " 



1370 



a 



= 18° 



Fig. 3. 



Fig. 3. Sketch map of the Bermuda volcanic mass. A, Argus Bank; 

 C, Challenger Bank; B, Bermuda Bank, on which the present islands are 

 shown. Numbers are depths in fathoms. 



The only point where information is wanting is the west 

 slope of the Argus Bank. On the southwest, south, southeast, 

 east, northeast, and north sides of the mass the slope is from 

 10-12 degrees ; the northwest slope is steeper, reaching its 

 maximum of 23 degrees off the Challenger Bank. The sound- 

 ings also show variations of slope in places, but these are minor 

 irregularities which need not be considered here. On the 

 north side the main mountain falls off 1,250 fathoms in 6 miles, 

 a slope of 14 degrees ; the Argus Bank 1,270 fathoms in 10 

 miles, a slope of 9 degrees. The low angles shown are indica- 

 tive of a cone built chiefly of basaltic lavas rather than of felsic 

 breccias and tuffs, and this accords with the results of the bor- 

 ing and with the slopes and petrographic character of other 

 great extrusive piles in mid-ocean, such as Hawaii and Samoa. 

 It is not intended by this to deny the possibility that breccias 

 and tuffs may make up a considerable portion of the mass ; the 

 steeper angles of slope of the smaller Argus and Challenger 

 volcanoes in places indicate that they may be largely con- 

 structed of fragmental material ; only that, taking everything 



