all the other groups which were deposited previously to it in the order of evaporation. These consequences are constantly verified in the saline beds which exist so numerously on the globe. Thus, to bring up again the two most important salts, numerous beds of gypsum are known, without rock-salt, or any of the other deposits, above them—which verifies our first conclusion; but no bed of rock-salt is known without gypsum—which verifies the second conclusion. More than this, a vast saline bed is now known which corresponds with the complete period set forth in our list—that is, with the complete period of evaporation; it is the formation at Stassfurt, Prussia, the disposition of which corresponds exactly with that shown in the list. The study of the Stassfurt bed further reveals an entirely new fact—the presence, in a part quite above the mean of deliquescent salts, of an important deposit of boracic acid combined with magnesium. All the geologists and engineers who have ever given their attention to the Stassfurt deposit have been unanimous in calling for volcanic intervention, and looking to the depths of the globe for the explanation of the origin of the boracic acid, and the place it occupies in the upper part of the bed; and they have all also given a more or less preponderant part to the play of volcanic agencies in the formation of the whole. This conclusion was the more natural, because the ordinary laws of chemistry seemed to oppose the probability of boracic acid, even if it existed, being found in the last mother-waters. Borate of magnesia is almost insoluble, and should have been among the first and lowest of the substances deposited. Adhering to the principle that there are no saline substances in the interior of the globe below the sedimentary formations, I silenced my protestations as a chemist, and applied myself to inquire if, contrary to all previsions, boracic acid did not exist in the ultimate mother-waters of the salt-marshes of the south of France. The result justified my geological induction to a degree beyond all possible anticipation. Not only does boracic acid exist in the ultimate mother-waters, but it exists there in a quantity relatively so considerable that a single drop of the water is enough to show it, either by the hydrogen method or by that of spectrum analysis. Thus, the presence of this substance in the upper part of the Stassfurt bed ceases to be an objection to the theory that the bed is purely and simply the result of the evaporation of the ancient seawaters; and its presence here furthermore gives a confirmation, as striking as unforeseen, to that theory.
My chemical and experimental studies are very far from constituting the only foundation for my theory of the sedimentary origin of the saline formations of the globe. Existing nature offers us in abundance, and on even a vaster scale than was shown in the ancient ages, phenomena which it is sufficient to analyze to bring forth anew, even to the slightest details, the manifestations which accompanied and determined the precipitation of saline matters in the estuaries of the an-
