is thus explained by the great French geographer, Elisee Reclus, in his
chapter on 'Le Plateau Central de la France.' [Footnote: See his
'Geographie Universelle,' vol. ii.: 'La France,' 1885.] 'There is no
doubt,' he writes, 'that at a remote period all these plateaux of
jurassic rock formed a single Causse, deposed by the sea in the
southern strait of the granitic group of France. Although the Causse
Mejean, placed almost in the centre of the series of plateaux, is a
hundred metres loftier than the rest, its formation accords with
theirs. All show the same features. From the banks of the Herault to
those of the Lot and the Aveyron, all show the same development of
continuous strata. The ancient glaciers spread on the highest summits
of the Cevennes as they melted, gradually cut into the rock, channelled
openings--finally, forcing their way through the layers, have formed
these gigantic defiles, now the marvel of geologists. If the rivers
flow in an unbroken stream in these deep gorges, on the contrary, water
is altogether absent from the plateaux above. The ground, riddled
everywhere into holes and fissures, is hardly moistened by a shower.
The rain, as if falling through a sieve, immediately disappears. In
some places the chasms of rock have widened, the intermediate
projections given way, and huge cavities of rightful depth--avens or
tindouls, as they are locally called--are formed in the limestone. But
the surface of the Causse is almost universally uniform, and these
subterranean wells are only indicated by slight openings. Nowhere a
foundation springs forth. Alike as to formation, aspect, and climate,
the Causses are unique in France.'

This entire chapter is a necessary preparation for no matter how hasty
a journey in the Lozere; equally to be recommended is the study of the
Causses by M. Onesime Reclus in his work 'La France.' [Footnote:
'L'orage aux larges gouttes, la pluie fine, les ruisseaux de neige