to the
Strait of Dover about the 1st of September and off the French coast
eastward of Cape la Hague about eleven days later. In the western area
the maximum temperature is about 15 deg. C. and occurs between September
1 and 11. The mean minimum surface temperature is between 5 deg. C. and
6 deg. C. at the eastern end, and increases to over 9 deg. C. off the
coast of Brittany. Owing to the thorough mixing of the water in the
eastern area the temperatures are here generally the same at all depths,
and the description of the surface conditions applies equally to the
bottom. In the western entrance, on the other hand, the bottom
temperature is often much lower than on the surface; the range here is
also much less, about 3 deg. C., and the maximum is not reached till
about the 1st of October, or from three weeks to a month later than on
the surface.

A detailed account of the mean conditions in the English Channel will
be found in _Rap. et proces-verbaux_, vol. vi., and _Bulletin
supplementaire_ (1908) of the Conseil Permanent International pour
l'Exploration de la Mer (Copenhagen). (D. J. M.)

_Cross-Channel Communication._--An immense amount of time and thought
has been expended in the elaboration of schemes to provide unbroken
railway communication between Great Britain and the continent of Europe
and enable passengers and goods to be conveyed across the Channel
without the delay and expense involved by transhipping them into and out
of ordinary steamers. These schemes have taken three main forms: (1)
tunnels, either made through the ground under the sea, or consisting of
built-up structures resting upon the sea bed; (2) bridges, either
elevated high above the sea-level so as to admit of the unimpeded
passage of ships under them, or submerged below the surface; and (3)
train ferries, or vessels capable of conveying a train of railway
vehicles with their loads. A tunnel was first proposed at the very
beginning of the 19th century by a French mining engineer named Mathieu,
whose scheme was for a time favourably regarded by Napoleon, but it was
first put on a practical basis more than fifty years later by J. A.
Thome de Gamond (1807-1876), whose plans were submitted to the French
emperor in 1856. This engineer had begun to work at the problem of
cross-Channel communication twenty years previously, and had considered
the possibility of a submerged tunnel or tube resting on the sea-level,
of steam ferries plyin