Coast of France and Bay of Biscay 
I have dwelt at some length on these two remarkable river channels, because they appear to be 
unique cases of valleys in which the streams from source to outlet have been unseen by man, and whose 
existence would have been unrecognised had not the sounding-line led to their discovery. 
Strait of Dover Watershed.—If we endeavoured to restore the condition of the Strait of Dover during 
a stage in the general elevation of the Glacial Period, we should find that the chalk formation which 
connects England with France forms a saddle of a minimum depth below the surface of the sea of about 
25 fathoms (150 feet), and that from this level the solid floor gradually slopes away westwards towards the 
Atlantic, and northwards towards the Arctic Ocean, thus constituting a water-parting. Down along its floor 
towards the Atlantic flowed the English Channel River, which we have just traced to its outlet ; and we 
might expect to find a corresponding channel sloping to the Arctic Ocean along the North Sea ; formerly 
conveying the waters of the Thames and other British streams, on the one hand, and of the Rhine, the 
Weser, and the Elbe, on the other, into the Arctic Ocean. But such an expectation would be doomed to 
disappointment ; for the solid floor of the North Sea has been “ the waste-heap ” for enormous masses of 
glacial refuse brought down from the Scandinavian Highlands, both by ice-sheets and by floating ice- 
rafts, at successive stages of the Glacial Period, and spread over the floor of the North Sea. By this 
means as well as by the silt of existing rivers, the old river channels, which undoubtedly exist, have been 
filled up and buried out of sight, and are generally unresponsive to sounding appliances." 
Over the region of the North Sea, from the shores of the British Isles and of Holland and Denmark 
to the Shetlands, the depth of the water seldom exceeds 80 fathoms, and this only on approaching the 
margin of the Continental Platform. This margin has been traced, by means of the isobathic lines and 
soundings, as passing by lat. 61° N. and long. 2° E. southwards, and by the late Cav. W. P. Jervis, as 
indicated by a steep valley following the coast of Norway as far as the Skager Rak, where the depth 
reaches 430 fathoms (2580 feet) opposite the northern promontory of Denmark. This descent represents 
the Continental Slope on the eastern margin of the platform off the British Isles. Cav. Jervis has 
endeavoured to trace a possible old channel for the Rhine valley, as passing between the Orkneys and 
Shetlands ; but the channel (‘ Palaeorhine”) is not very clearly indicated on the charts.? 
The Loire—This river, in its submerged portion, traverses the Continental Platform where its 
breadth is about 100 miles. Its channel has been silted up, so that there is difficulty in tracing its course 
by means of the soundings for some distance from its mouth. Indications, however, may be observed 
south of Belle Ile, and again at a distance of 50 or 60 miles farther west in long. 4° 10° W. From 
long. 5° 30’ the channel is fully developed, and may be traced continuously by the deepening of the 
soundings below the general floor of the platform to its outlet, where it takes the form of a double 
cafion with which it passes down to the abyssal floor at a depth of about 1500 fathoms.® 
The Gironde (Garonne).—A well-defined bay pointing N.E. breaks through the margin of the 
Continental Platform in long. 2° 40’ W. and lat. 44° 55’ N., which may be inferred to be the outlet 
of this large river, which enters the ocean at a distance of 70 miles from its present mouth, but owing to 
silting cannot clearly be connected. The relative positions of the gap and the present embouchure seem 
to justify the inference. 
The Adour.—OFf all the submerged river channels to be met with along the coast of Western 
Europe, none is more strikingly developed than that of the Adour.‘ 
This fine river has its source amongst the highest valleys of the Pyrenees and enters the ocean at the 
base of this range near Bayonne. It is unique in this respect, that its submerged channel is continuous 
with the existing stream from its present mouth to its former outlet at a distance of about 100 miles from 
1 The direction of the flow from the Norwegian Uplands will be seen by reference to Plates VII. and VIII. 
* Jervis, “'Thalassographical and Thalassological Notes on the North Sea,” Trans. Vict. Inst. vol. xxxii. P+ 317 (1900). 
8 gooo feet—an unusual depth. 
4 Dr. Nansen in his work on the Polar Ocean (vol. iv.), when describing the submerged river-valley of the Adour, says: “It is almost 
impossible to give any other explanation of its existence than of a former river-vall 
8 
ey at a time when the whole region was elevated into land.” 
