520. The carbonate calcareous earth is the whole earth, not the corrosive. This is only the half of the earth-element, only its basic or phlogistic principle. What has been called pure calcareous earth is a half earth; the perfect or naturo-historical earth is just that which is chemically impure. 521. The calcareous earth is not, however, perfected with one position. It still exhibits several stages of development which appear to be approximations to the salt, e. g. Strontian and Baryta. 522. The silicious earth, which principally represents the Earthy, holds its principles more firmly together. No separation occurs there in the carbonic acid and the basic or corroding body of earth; no association with water, no great activity, no direct participation in the highest evolutions of the planet; but it continues to lie in an extreme state of contraction, and in a state of indifference in the non-differencing darkness. 523. This pure earth is the basis, the pedestal of all the other earths, and the foundation of the planet; for it alone is the earth proper, the earth-abiding earth-element, while the other masses of earth, divided in their principles, have pitched themselves in outward opposition to the sun and other elements. The silicious earth is in every respect the centre of all earthy productions, these being only digressions from it. The Zircon earth is only a removal or displacement of the silicious toward the argillaceous earth. 524. The argillaceous earth also is not dissevered into its principles; it is not found as a carbonate. On the contrary, it is at once shown to be far more pliable by its capacity for being kneaded and moulded in water, and by its hardening when exposed to air and fire. It is also seized upon and dissolved, i. e. reduced to the aqueous condition, by all acids. Its kindred earths are the Glucine and Yttria, verging towards the talcose earths. 525. The first dismemberment of principles is shown by the talcose earth. Where it appears uncombined with the former earths it is carbonate, yet still feebly corrosive. 526. These three principal earths together make up the body of the earth, while the calcareous earth is only spread over them like a mantle or crust.