Page:A Treatise on Geology, volume 2.djvu/33

 CHAP. VI.

On reducing the inclination to 1° there was still a perceptible movement. This table may be compared with Professor Forbes's measures of the velocities observed in the Mer de glace already given.

Collected in the atmosphere, the rain is filtered through the sandy rocks, passes rapidly by the joints of the calcareous strata, and is stopped by the clays, and by dykes and faults; it then issuing in springs. But it is no longer the same water: rain water is, indeed, far from being in a state of purity; it contains always carbonic acid, frequently some muriatic acid or chloride of sodium, besides other irregular admixtures. In passing through the rocks it absorbs lime, oxide of iron, &c., and on issuing in the form of springs, loses its excess of carbonic acid, and again deposits carbonate of lime, carbonate of iron, &c. From some springs the quantity of carbonate of lime deposited is enormous; with the water of others, sand, gravel, fossil shells, and zoophytic fragments issue. Thus the first operation of water in and upon the earth is the same, viz. to consume away the solid substance of the rocks, and either deposit it in new situations not far from the source, or deliver it to flowing streams to be carried further away.

Springs which have an impeded issue to the surface are the most general cause of landslips: we may

Goldau.