Volume 183502

Principles of geology, being an attempt to explain the former changes of the earth's surface, by reference to causes now in operation / [Sir Charles Lyell].

  • Charles Lyell
Date:
1835
Catalogue details

Licence: Public Domain Mark

Credit: Principles of geology, being an attempt to explain the former changes of the earth's surface, by reference to causes now in operation / [Sir Charles Lyell]. Source: Wellcome Collection.

    33/472 page 19
    before muriate of soda can, in like manner, be pre- cipitated, the whole Mediterranean ought, it is said, to become as much saturated with salt as Lake Aral, the Dead Sea, or the brine-springs of Cheshire. It is undoubtedly true, in regard to small bodies of water, that every particle must be fully saturated with muriate of soda before a single crystal of salt can be formed; such is probably the case in all natural salterns; such for example as those described by travellers as occurring on the western borders of the Black Sea, where extensive marshes are said to be covered by thin films of salt after a rapid evaporation of sea-water. The salt ééangs of the Rhone, where salt has sometimes been precipitated in considerable abundance, have been already mentioned. But whether it be necessary that every part of a sea of enormous depth should be fully saturated before any precipitate can take place is a question of some difficulty. In the narrowest part of the Straits of Gibraltar, where they are about nine miles broad, between the Isle of Tariffa and Alcanzar Point, the depth varies from 160 to 500 fathoms: but between Gibraltar and Ceuta, Captain Smyth sounded to the enormous depth of 950 fathoms ; where he found a gravelly bottom, with fragments of broken shells. Saussure sounded to the depth of two thousand feet, within a few yards of the shore, at Nice, and M. Bérard has lately fathomed to the depth of more than six thousand feet in several places without reaching the bottom.* The central abysses of this sea are in all likelihood at least as deep as the Alps are high, and, as at the depth of seven hundred fathoms only, water has been - * Bull. dela Soc. Géol. de France. — Résumé, p, 72. 1832.
    digitised image 1
    digitised image 2
    digitised image 3