MAPS AS GEOGRAPHICAL ILLUSTRATIONS 499 
Further down, the valley has been more widened, forming the 
present estuary; here all traces of the (presumable) primitive 
lobes and meanders are destroyed. Thus, to a very limited 
extent, the action of marine currents in excavating valleys, gen- 
erally accepted as the sole process of origin early in this century, 
still deserves consideration in the lower valley of the Seine. 
The coast of this region gives a remarkably good example of 
a long continuous sea cliff, of very moderate irregularity, in the 
production of which the original outline of the land has been 
completely destroyed. This is the best example of a thoroughly 
simplified, mature coast line that I have found. The recession 
of the coast has been so great that the lower trunks of a number 
of small rivers have been consumed, leaving the upper branches 
now to enter the sea as independent streams. Rivers of this 
kind may be said to be ‘“‘betrunked” by marine erosion; they 
are easily distinguished from rivers that are betrunked by sub- 
mergence. The smaller valleys are cut across in mid-height on 
the cliff face; their deepening not having kept pace with the 
recession of the cliff, in spite of the strong fall at their lower end. 
The large proportion of underground drainage through the chalk 
of the upland has probably much to do with this result. 
Villages on the coast are found only where the larger streams 
have deepened their valleys to sea level. St. Valéry-en-Caux 
and Fécamp are good examples. Between these valleys, the 
cliffed coast is absolutely harborless and inaccessible. Jetties 
are constructed at the valley-mouths to keep the stream-inlets 
clear ; but they are rapidly clogged with the shore drift of chalk 
flints. 
THE CHAMPAGNE. 
Sheets 33, 34, 49, 50, 66, 67. 
The lowland of the Champagne lies on the Cretaceous forma- 
tion, enclosed by the Tertiary escarpment of the Ile de France 
on the west, and descending by a lower escarpment of chalk to 
the humid Champagne belt on the east. The strata are gently 
™ An excellent account of the physiography of this region is given by de Lapparent. 
Lecons de Géographie physique, Paris, 1896, 396. 
