NOTES. 461 



h6llows of such frequent occurrence in gypsum districts. The limestone strata, 

 besides being " loaded with the exuviae of innumerable generations of organic 

 beings," says Dr. Buckland, " afford strong proofs of the lapse of long periods of 

 time, wherein the animals from which they have been derived, lived, and multiplied 

 and died, at the bottom of seas which once occupied the site of our present con- 

 tinents and islands." * With how much reason then may we not suppose those 

 formations to have held large beds of rock salt, which the percolation of water, in 

 the lapse of ages, removed, and left the chambers empty, or the receptacles of 

 meteoric water. The percolation of water through felspar rocks, must of necessity 

 wash away the alkaline ingredient, which combining with iron will form hydrate, 

 or by its decomposition oxidate the metallic substance. Hence result chalybeate, 

 acidulous, sulphureous, and saline springs, all the result of capillary attraction in 

 the strata of the earth, and the disintegration by water of the various ingredients 

 which the universal solvent holds in a state of fluidity. 



Supposing these cavities, to which we have just referred, to have been freed from 

 their original salt deposits, by water percolating the fissures leading to and from 

 the masses of salt, we trace the operation of salt springs. For in all cases in which 

 water holds any mineral in solution, it acts by combination, but where it simply 

 destroys the mineral aggregation, the mineral falls into small pieces with an audible 

 noise, as is observed in bole ; or it falls without noise into small pieces, which are 

 soon diffused through the fluid, without either dissolving in it or becoming plastic, 

 as in Fuller's earth, and some minerals, as unctuous clay ; it renders plastic other 

 minerals, absorbs water in greater or less quantity, by which their transparency, 

 and also their colour, are changed. 



The toadstone, which intersects mineral veins, totally cuts off all communication 

 between the upper and lower fissures, and by the closeness of its texture permits 

 not the water in the clay strata, or way-boards, to filtrate. Hence toadstone is 

 said to be capable of turning water, as we have shown in the shaft and gallery, 

 o a G G. Sandstone strata, of an open porous texture, becomes a great feeder 

 of water. Several of the sandstones are, however, impervious to water, and 

 almost all the beds of light-coloured argillaceous schistus, or fine clays, are 

 particularly so, being very close in their texture. But the percolation of water 

 at the beds or partings of two strata is an occurrence so general, that our 

 wonder ceases when examining parts of the country where the strata basset or 

 shoot to the surface in an acute angle, to find the alluvial covering in places 

 swampy, marshy, and overrun with puddles, springs, and all that species of soil, 

 which, being damp and cold, subjects its inhabitants to rheumatism, agues, and a 

 train of diseases, unknown in regions that are not incumbent on the extremities of 

 way-boards and capillary strata. The source or feeder of these subterranean 

 capillaries receiving a constant supply, keeps up the train of human ills from one 

 generation to another, while local interests or associations bind the natives to their 

 hereditary doom. 



Capillary attraction and cohesion, besides expounding the phenomena of fluid 

 ascent in strata of earth, direct us in penetrating those troublesome quicksands and 

 beds of mud, which in the winnings of collieries are met with in mining, and where 



* Dr. Buckland's Bridgewater Treatise, pp. 112-116, 1st ed. vol. i. 



