276 



TEOF. E. HULL, LL.D., ETC.^ ON THE SUB-OCEANIC 



ehoAV that, the slopes from the edgie of the Continental Plat- 

 form to the base are in general qin'te comparable with those 

 of land escarpments. For the pm'pose of determining this 

 point I have drawn by means of co-ordinates where the 

 soundings admit, nine sections, and plotted them to a natural 

 scale. In doing so I have only taken those of the outer 

 slopes ; but if I had also included the sides of the canons, or 

 old river-valleys, the results in the direction of steepness 

 would have been much greater. As a general conclusion we 

 may take the average slope at 13° to 14° ; varying from 5° 

 to 36° or even more. The walls of the submerged canons or 

 river-valleys are, hoAvever, often precipitous, sometimes 

 vertical, faces of rock. The folloAving table shows the 

 results of the soundings : — 



No. 



Table sho\ying Approximate Slopes of the 

 (jREAT Declivity. 



Position. 





Vidal Bank, 



Lat. 



La Chapelle Bank, ,, 



Bay of Biscay, „ 

 Promontory of Brest „ 



)) )> 5> 



Off C. Penas, 



Off C. Ortegal, 



Off C. Torinana, ,, 



Off Oporto, „ 



55° N. 

 54° N. 

 47° 30' 

 47° 20' 

 48° 10' 

 46° N. 

 44° 20' 

 44° 5' 

 43° 4' 

 41° 5' 



Off the coast of Spain and Portugal the descent to the 1,000 

 fathom contour is generally steep and is varied by numerous 

 bays and headlands; but owing to the fewness of the sound- 

 ings, as for example off Vigo Bay, the features cannot be traced 

 Aviththat degree of detail which is possible in the British and 

 French waters. Off the north coast of Spain the declivity is 

 characterised by several precipices comparable with some 

 amongst the Alps and other mountain cliains. Thus off 

 Cape Bidio, there is a descent of about 8,000 feet in four 

 miles; another off Cape Ortegal of about 13,000 feet in the 



