rjVER VALLEYS OF THE WEST AFRICAN CONTINENT, ETC, 155 



are of special interest as tending to confirm tlie conclu- 

 sions arrived at by myself in this and preceding commmiica- 

 tions. 



1. The Submerged Channel of the Ehro. — The number of 

 soundings off Cape Tortosa is not as numerous as might be 

 wished for the purpose of determining the course of the 

 submarine channel of this river ; still, the inward bend of 

 the contours from that of 40 fathoms dowm to that of 

 1,000 fathoms, immediately opposite the mouth of the river, 

 cannot be mistaken as indications of the course of the 

 channel.*' Along the Gulf of Valencia the representative 

 of the Continental Shelf is unusually broad and well 

 defined, breaking off at the 100-fathom contour at a 

 distance (opposite Valencia) of GO miles from the coast, and 

 with a very steep descent for a depth of 500 fathoms. 



2. Channel of the Rhone. — The submarine channel of the 

 Khone is perhaps even more definitely indicated than that 

 of the Ebro by the inward bend of the isobaths, extending 

 from 100 to 1,200 fathoms. The channel commences directly 

 south of the city of Marseilles at a distance of about 30 

 miles to the east of the point where the river itself now 

 enters the sea ; but it is in a direct line with the course of 

 the main stream below Aries ; and between the two points 

 the submerged channel may be supposed to pass along the 

 Continental Shelf; though not apparent owing to silting up, 

 HS is usual at the embouchures of large rivers. The shelf 

 itself is here of considerable breadth — varying from 50 to 

 25 miles in the Gulf of Lyons, and limited by the 100- 

 fathom contour. 



3. Submerged River Valleys of the Gidf of Genoa. — The 

 remarkable series of submerged river valleys continuous 

 with the rivers which descend from the Apennines into the 

 Gulf of Genoa (the Ligurian Sea) have been determined 

 by Professor Arturo Issel, of the University of Genoa, and 

 are of peculiar interest both from their number and also 

 from the light they throw upon the geological age of these 

 submarine channels. These river-channels were described 

 as far back as 1887 by Professor Issel, and subsequently ni 

 two other publications ; but have not received, at least 

 in this country, the attention they have deserved. I, 



* The sounding "928" without touching bottom, and in close proximity 

 to one of 137, wliich has done so, indicates a very steep slojie for the 

 ■western margin of the channel (see Chart No. 2158a). 



