150 I'KOF. K. HULL, LL.D., F.R.S., F.G.S., ON THE SUJS-OCEANIC 



tliorofore, feel great satisfaction in beiui;' tlic chaiinel for 

 l)ringing tliein before an Englisli-speaking audienee'.* 



The soundings upon which the detennination of the 

 submerged valleys depend were carried out by Capt. 1. [^. 

 Magnaghi in the ship " Wasln'ngton," of the lioyal Italian 

 Navy, and were laid doAvn on a chart which enabled Professor 

 Issel to trace the isobathic contours by which the submarine 

 features of the ground have been portrayed. It was found 

 tliat the sinuosities became especially well defined along the 

 contour of 200 metres (about 110 fathoms) which marks the 

 edge of the Onitinental Platform at a distance of about 

 7 miles from the coast ; they are called " Sinuosites pro- 

 fondes" and are always directed towards the coast. 



The contour line of 500 metres passes 25 miles to the south- 

 west of Spezia ; that of 1,000 metres is irregular and rues 

 at variable distances of 8 to 14 miles from the coast; 

 all, however, are "notched" by sinuosities of the submarine 

 valleys.f But the point of special interest is the fact that 

 all these submarine channels are actually, or inferentially^ 

 continuous with those descending into the sea along the 

 coast of Liguria and having their sources in the Maritime 

 Alps. The following are named by Professor Issel, viz. : — the 

 Basagno, Polcevera, Giuliauo, Aquila, Merula, Arma, and the 

 Koida; these streams keep their chaimels under the sea in 

 the same directions as upon the land, and can be distinctly 

 followed to a depth of 900 metres, or nearly 500 fathoms. 

 These observations lead the author to the conclusion that 

 there has been an elevation of the whole region of Liguria 

 to the extent of *J0() metres (about 3,000 feet), at a recent 

 period (« luie ejtofjne recente) — in other words Post-Tertiary 

 — a conclusion in harmony with that arrived at by myself 

 and other observers on other grounds. lUit I must here 

 state the grounds of this conclusion as given by Professor 

 Issel himself. 



* Professor Issel's observations on the submerged valleys of Liguiia 

 were first i»ublislied in the Comptes Rendus cles Sciences, Nos. 24th 

 and 31st .Jainiary, 1887 ; then in his work, // Teiremoto del 1887 in 

 JJyun'a (Geuova), and again in his work, Liguria Geologica e Preistorica 

 (2 vols., Genova, 1892). 



t I have myself endeavoured to trace these contours on the Admiralty 

 Chart (No. 2158a), but tlie scale is too small to admit of a detailed 

 representation of the small river valleys descril)ed by Professor Issel, ami 

 leads me to conclude that, with maps of suHiciently large .scale and 

 numerous sounding.s, many streams entering the Mediterranean nught 

 show their underground channels. 



