CHAPTER III 
Coast of France and Bay of Biscay with Submerged River-Valleys 
EXPLANATION OF PLATES II anp III 
N the previous chapter I gave a general description of the widespread platform from which rise the 
British Islands and Western Europe. But in Plate II. we are confronted with the remarkable 
phenomena that this platform is trenched not only by the submerged valleys of rivers descending to the 
sea from the bordering emergent lands, and which are visible to us through part of their course, but 
also by the channels of some streams which rose from land now beneath the ocean ; have never been seen 
by the eye of man, and which.would never have been discovered by him but for the invaluable aid of 
the soundings. These latter streams are included within the area of the British Seas, and to them I have 
given the names of “The Irish Channel River Valley” and the “English Channel River Valley” 
respectively. Of their existence there can be no doubt whatever ; and for this we have the authority of 
Professor Spencer derived by a similar process to that which led to their discovery by myself.!_ We shall 
consider these latter channels, as being the most northerly and close to our shores, before proceeding to 
the former and more distant cases. 
The Irish Channel River Valley—This channel begins to be traceable opposite Milford Haven, 
though it probably has its origin much farther north, but is apparently silted up under the stagnant waters 
of the Irish Sea. Opposite the entrance to the Bristol Channel a distinct arm is thrown out which we may 
well infer to be the submerged portion of the Severn, which thus became a tributary to the river. Thus 
the combined streams, augmented by those from the south-east of Ireland, must have produced a river of 
considerable volume which pursued a rather serpentine course of over 250 miles across the Continental 
Platform till it descended with a double outlet into the outer ocean. 
The North Channel Submerged River Valley—There is known to bea river channel in the narrow strait 
between the coast of Antrim and Scotland which, when the Irish Channel Tunnel scheme was first 
projected, caused anxiety to the promoters, as the depth of its bed, filled with glacial mud and silt, was 
unknown and could scarcely be determined ; it lay right in the way of the proposed tunnel to connect 
Ireland and Scotland. It is in all probability correct to say that this hollow is the channel of a former 
river; but the soundings do not enable us to infer whether the stream ran northwards into the ocean or 
southwards to join the Irish Channel River. 
The English Channel River —If the course of the Irish Channel River was tortuous this was not the 
case with its counterpart of the English Channel. Through a distance of about 300 miles from its rise 
somewhere near the Strait of Dover to its exit at the margin of the Continental Platform, the river 
pursued its nearly straight course, till its waters issued forth on the ocean through a well-defined ever- 
deepening cafion in the meridian of 7° W. 
North of Cherbourg it appears to have received the waters of the Seine in a submerged channel of 
no great depth, and the streams entering the Solent in all probability formed a junction with the main 
channel above the meeting of the Seine. Thus augmented, the river entered on that part of its course 
marked on the chart as “‘ The Hurd Deep ”—a well-defined channel of 70 miles in length which, at its 
upper end, is about 186 feet in depth, at its centre 336 feet, and at its lower end 162 feet below the 
general level of the valley-floor. Along this part of its course the river channel has been kept clear by 
the strength of the tidal current, owing to the narrowness of the present channel between England and 
France. But above and below the Hurd Deep the English Channel widens considerably ; owing to 
which the old river cafion has been silted up until, on approaching the margin of the Continental Plat- 
. form, it again becomes recognisable by the soundings, and it enters the ocean between lofty walls of rock. 
1 American Geologist, vol. xxxv. (1905). 
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