Werner considered all rocks as having originated by crystallization, either chemical or mechanical, from an aqueous solution--a universal primitive ocean. He was a Neptunist, as opposed to the Vulcanists or Plutonists, who believed in the existence of a central fiery mass. Werner thought that the earth showed universal strata like the layers of an onion, the mountains being formed by erosion, subsidence, cavings-in. In his judgment granite was a primitive rock formed previous to animal and vegetable life (hence without organic remains) by chemical precipitation. Silicious slate was formed later by mechanical crystallization. At this period organized fossils first appear. Sedimentary rocks, like old red sandstone, and, according to Werner, basalt, are in a third class. Drift, sand, rubble, boulders, come next; and finally volcanic products, like lava, ashes, pumice. He was quite positive that all basalt was of aqueous origin and of quite recent formation. This part of his teaching was soon challenged. He was truer to his own essential purposes in writing a valuable treatise on metalliferous veins (_Die Neue Theorie der Erzgänge_), but even there his general views are apparent, for he holds that veins are clefts filled in from above by crystallization from aqueous solution. Before Werner had begun his teaching career at Freiberg, Desmarest, the French geologist, had made a special study of the basalts of Auvergne. As a mathematician he was able to make a trigonometrical survey of that district, and constructed a map showing the craters of volcanoes of different ages, the streams of lava following the river courses, and the relation of basalt to lava, scoria, ashes, and other recognized products of volcanic action. In 1788 he was made inspector-general of French manufactures, later superintendent of the porcelain works at Sèvres. He lived to the age of ninety, and whenever Neptunists would try to draw him into argument, the old man would simply say, "Go and see."