Terraces and River Valleys — Spencer. i6l 
would not expect the features to be so well defined in the 
confined basin as in the Atlantic, especially the declivity- 
descending from the platform. Along the gulf of Valentia 
the continental platform is unusually broad reaching sixty 
miles in width, where it breaks ofif suddenly at about a hun- 
dred fathoms. Indenting the shelf and declivity from 240 
feet to a depth of 6.000 feet, a valley is traceable opposite 
the mouth of the Ebro. But the soundings are not suf- 
ficient for showing the detail. In front of the mouth of the 
Rhine, where the shelf varies from 25 to 50 miles, and lim- 
ited by about the lOO-fathom line, the isobaths of the de- 
clivity show the course of the valley to a depth of 7,200 feet. 
But the most important discoveries of such valleys 
were made in the gulf of Genoa by Prof. Arturo Issel of the 
University of Genoa.* The continental platform has a 
breadth of seven miles and is defined at a depth of 660 feet, 
where the edge is indented with many sinuosities. These 
notches of submarine valleys are also shown at depths of 
500 and 1. 000 metres. This last depth is reached at from 8 
to 14 miles from the coast. Prof. Issel has worked out the 
channels as the submarine continuations of seven rivers to 
a depth of 900 metres, or about 3,000 feet, and concludes 
therefrom that a late elevation to that amount obtained. 
The land portion of some of these valleys has been exca- 
v^ated out of the Eocene formations, or in some cases out of 
the Pliocene, Miocene and the Eocene, all three, showing 
their age to be Pleistocene. But doubtless the maximum 
depth of the valleys had not been reached. Here is addi- 
tional confirmation of the age of the late elevation of west- 
ern Europe, arrived at in a most satisfactory manner. The 
erosion of those wide, deep valleys, excavated since the Pli- 
ocene, involves a lapse of time of long duration much 
greater than has been granted by many of us for the Pleis- 
tocene period. 
Cavaliere Jervis, of Turin, calls attention to Pliocene 
clays occurring at an altitude of 1,640 feet at Pianfei (Cu- 
neo). Such commonly skirt the Apennines from one end 
to the other, and are overlaid to a considerable elevation 
with Pleistocene clays and sands. But in Sicily the Plio- 
* Comptes Rendus des Sciences. Nos. 24th and 31st. Jan. 1887. 
