Falling in Love, page 249 by Grant Allen
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way it is still being deposited in the evaporating waters of many inland seas. Every schoolboy knows of course (though some persons who are no longer schoolboys may just possibly have forgotten) that the Caspian is in reality only a little bit of the Mediterranean, which has been cut off from the main sea by the gradual elevation of the country between them. For many ages the intermediate soil has been quite literally rising in the world; but to this day a continuous chain of salt lakes and marshes runs between the Caspian and the Black Sea, and does its best to keep alive the memory of the time when they were both united in a single basin. All along this intervening tract, once sea but now dry land, banks of shells belonging to kinds still living in the Caspian and the Black Sea alike testify to the old line of water communication. One fine morning (date unknown) the intermediate belt began to rise up between them; the water was all pushed off into the Caspian, but the shells remained to tell the tale even unto this day.
Now, when a bit of the sea gets cut off in this way from the main ocean, evaporation of its waters generally takes place rather faster than the return supply of rain by rivers and lesser tributaries. In other words, the inland sea or salt lake begins slowly to dry up. This is now just happening in the Caspian, which is in fact a big pool in course of being slowly evaporated. By-and-by a point is reached when the water can no longer hold in solution the amount of salts of various sorts that it originally contained. In the technical language of chemists and physicists it begins to get supersaturated. Then the salts are thrown down as a sediment at the bottom of the sea or lake, exactly as crust formed on the bottom of a kettle. Gypsum is the first material to be so thrown down, because it is less soluble than common salt, and therefore sooner got rid of. It forms a thick bottom layer in the bed of all evaporating inland seas; and as plaster of Paris it not only gives rise finally to artis