Page:A book of the Cevennes (-1907-).djvu/44

22 Haute Loire, through which it makes its way till it leaves it for Forez. The Loire rises 4,500 feet above the sea, and when it quits the department it has fallen to 1,450 feet. When the volcanoes of Le Velay were in eruption and the tableland was overflowed with molten lava, the Loire must have been arrested and have mounted to heaven in a column of steam. In time the lava cooled, and the stream groped for beds of scoria and fallen dust through which it could nibble its way with ease. But when it encountered a barrier of basalt the case was altered. This blocked its course as with rows of iron piles rammed into the ground and running far back. But the crystallisation of the lava into basaltic prisms helped the river to break through.

The molten matter, of the consistency of treacle, flowing over the country followed its undulations, filling hollows here and rounding obstructions there. When it cooled it began to crystallise, and form hexagonal columns that are upright. But when the surface of the original soil would not allow of regular crystallisation, there the columns shaped themselves in all directions and in great confusion; the result being that in many places the basalt was fractured, fissured, and ruinous from the very first. The water speedily detected these weak points, worked at them, tumbled the columns down, overleaped them, bored further, and did not rest till it had cut its way completely through the barrier.

Hercules in his cradle strangled a couple of serpents, and the infant Loire, a ridiculously small stream for the work it effected, on entering the department laid hold of and split the bed of Plutonic deposit, and held on its way between basaltic escarpments. It is, however, below Le Puy, after the Sumène has entered it, under