Page:Popular Science Monthly Volume 21.djvu/847

Rh such a temperature in the presence of water without being decomposed.

As the process of cooling continued, the atmosphere kept incessantly yielding by condensation the water which it held, and this water kept perpetually dissolving the soluble salts which it found already present, and also those that were continuously produced by the action of the acids it bore with it. As we have already seen, these salts were sulphates and chlorides. On the other hand, the metals competent to combine with the sulphur and the chlorine were necessarily those existing in the rocks that formed the first crust of consolidation, and these metals were, as we shall be able to show, lithium, potassium, sodium, magnesium, and calcium. Now, it is these five metals which, united with chlorine and sulphur, constitute nearly the total amount of the salts dissolved in the waters of the seas. Such, to my mind, is the origin of the salts which mineralize the seas; and it is an origin wholly exterior. Thus, from the most ancient aqueous period of our planet, from the time when its external temperature was not notably below the boiling-point of water, and from a time, consequently, before any trace of life was possible, the seas have had essentially the same composition they have to-day. Zoölogists have for a long time regarded this fact as necessary, because the animals whose remains have been found in the most ancient sedimentary beds did not differ as to their general plan from their congeners in modern seas, and could not, consequently, have lived in waters that differed sensibly in composition from the water of existing seas.

If the whole mass of chlorides and sulphates was originally dissolved in the sea-waters, then the only way we have of explaining the origin of the saline formations which exist in the sedimentary beds is to assume that they have been left by the spontaneous evaporation of parts of the ancient seas accidentally isolated from the oceans. I came to this conclusion long ago, not by a more or less intuitive suggestion, but drawn to it by the logic of facts and the ideas I am about to present. This conclusion once formulated, I have taken the consequences, as numerous as important, which it involves, and have submitted them to an experimental verification.

In approaching the experimental side of my investigations, I had first to study in its details what takes place when the waters of existing seas are left to spontaneous evaporation.

First, a very weak precipitation occurs of carbonate of lime with a trace of strontium, and of hydrated sesquioxide of iron, mingled with