154 PROF. E. HULL, LL.D., F.K.S., F.G.S., ON THE SUB-OCEANIC 



PART 11. 



The Mediterranean Basin — Submerged River Valleys. 



That tlie IMediterranean Basin, at least in its western 

 portion, nnist have partaken in the great vertical oscillations 

 which have affected the regions bordering Western Enrope 

 and the continent of Africa requires no proof. The general 

 elevation of the ocean-bed and adjoining lands to the extent 

 of 7,000 or 8,000 feet throngh a distance of over three 

 thousand miles must have influenced the regions embracing 

 the Mediterranean and bordering countries. But while this 

 is the case, it is not to be expected that the physical features 

 of the submerged lands should be as clearly developed 

 within the confined area of the ]\Iediterranean Sea as along 

 the shore of a great ocean extending for thousands of miles 

 in two directions, and exposed to tlie action of prevalent 

 westerly winds originating powerful wave action on the 

 opposing coast. To such action we owe the cliff's bordering 

 the British and Continental coast along the Atlantic, the 

 formation of the Continental Shelf, and the stupendous line 

 of cliff's by which it is bounded.* These features, however, 

 are not so clearly defined within the Mediterranean area, if 

 at all in some parts ; but the submarine coast is found to 

 descend into deep Avater by a broken slope, continuous with 

 the bordering lands down to a depth of 1,000-1,200 fathoms, 

 when it gives place to the abyssal region, Avhich descends to 

 deptlis of over 1,500 fathoms. As a consequence of this, and 

 as we might a priori expect, the submerged river valleys are 

 also less clearly defined than those off the coast of France, 

 Spain, Portugal, and, Ave may add, of West Africa. 



The submerged channels which I have succeeded in 

 tracing on the Admiralty Charts are those of the Ebro and 

 Rhone, as also that of Admiral Spratt between " Adventui'e 

 Bank" and Cape Bon; but 1 Avill take this o})portuiiity of 

 bringing before the members of the Institute the remarkable 

 discoveries of similar channels made by Professor Arturo 

 Issel oft" the northern coast of the gulf of Genoa, which 



* It may seem strange that tliesame causes, namely, vertical movement 

 of the crust and wave action along the border of the ocean, should have 

 produced two such dissimilar features as the Continental Platform and 

 the Great Declivity, but it can be shown that this is so ; the difference 

 in the features being due maiidy to the relative duration, or length of 

 time between the two components above referred to. 



