284 PROF. E. HULL, LL.D.^ ETO., ON THE SUB-OCEANIC 



five or six miles immediately south of Cape Razon. Like 

 several of the canons of the Lirger rivers already described — 

 that of the Tagns is characterised by a double outlet, forming 

 in plan a Delta. After descending from its apex for a distance 

 of 35 miles in a westerly direction, and to a depth of (500 

 fathoms, the channel divides; one branch, which is the deeper, 

 continuing very much in the same direction ; the other, sweep- 

 ing round in a semicircle to the north-west, and ultinjately 

 entering the deep ocean at a distance of about 15 miles from 

 the mouth of the former chainiel. There is thus enclosed a 

 large isolated tract — the highest part of which rises to 

 within 6(3 fathoms of the Bresent surface of the ocean. 



1. 



Towards the mouths of these channels the waters of the old 

 Tagus must have entered the ocean in a series of cascades 

 Avitli :i total descent of over 5.000 feet within a distance of 

 about six or seven miles;* and considering the vast volume 

 of water brought doAvn by the Tagus at the present day, 

 such a series of falls must have been grand in the extreme, 

 because to the present volume of water must be added that 

 of the Platform itself. 



Other submerged channels of minor importance might be 

 referred to, but the above will probably be considered 

 sufficient to give some idea of the njagnitude and grandour 

 of the features now lost to view beneath the waters of the 

 ocean — but happily capable of being "summoned from the 

 vasty deep " and idealized by means of tlie sounding line ! 



VII. Isolated rocks and Sea-stacks.— Amongst the 

 physical features by which the Great Declivity was diversified 

 the most conspicuous were probably the isolated rocks and 

 sea-stacks which rose from the ocean floor. One of these 

 occurs about 36 miles off Cape Eazo in the submerged valley 

 of the Tagus, rising from 500 fathoms of water with the 

 summit 110 fathoms; its heieht was therefore 2,340 feet. 

 (Plate HI.) 



Part III. 



I. Geological Age and mode of formation of the 

 SUBMERGED PHYSICAL FEATURES. — The fact that the sub- 

 merged river-valleys are in most cases merely prolongations 

 of those of the adjoining lands is a sufficient indication that 

 the physical features above described are geologically of 



The soundings show a descent from 600 to 1,200 or 1,300 fathoms. 



