Complete Works, Vol. V

Recall those things which were determined in the preceding books of natural science, namely that the stars, by their quantity, light, position, and motion, move and order the world according to all the matter and place of things that are generated and corrupted. Indeed, the power thus determined by the stars is infused into the place of generation for each thing, in the manner determined in the natures of places. For this power is productive and generative of every element and of everything made of elements.

This power of the place is gathered from three powers, of which one is the power of the mover of the moved orb. The second is the power of the moved orb itself, with all its parts and the figures of those parts that result from the position of parts looking at each other in diverse ways, due to the manifold speed and slowness of the movers. The third, however, is the elementary power, which is hot, cold, moist, and dry, or a mixture of these. The first of these powers is as a form directing and forming everything that is generated, just as the power of art relates to the matter of the artifact. The second is like the operation of a hand. And the third is like the operation of an instrument moved and directed by the hand toward the end intended by the artist. And therefore Aristotle said that every work of nature X is a work of intelligence: for the place receives these powers just as the womb receives the formative power of the embryo.

This power, therefore, determined for the generation of stones, exists in earthy or watery matter, in which all places where stones are generated converge. For just as in animals that are generated from putrefaction, a life-giving power is infused from the stars, so it also happens in the matter of stones, that a formative power of stones is infused by the said method. Therefore, in whatever place unctuous earth is mixed through vapor reflected back into itself, or in which the powers of the earth apprehend the nature of water and draw it toward dryness, and incline vehemently, there is certainly the place of the generation of stones. For this reason, solid surfaces of the earth, from which such vapor

cannot exhale, generate many stones. But in soft, ashen earth, which infects water rather than apprehending it in its properties, stones cannot be generated. And this is the cause why many stones are generated on the banks of eternal rivers: for such banks are most solid, enclosing within themselves the elevated vapors. Those banks are also vaporous, because the heat excited by the reflection of its light upon the waters is repelled by the coldness of the water toward the shore, and being entangled in parts of the earth, it decocts and hardens the earth mixed with water.

Truly, from the same cause, the bottom of such rivers becomes stony, because the heat penetrates the shores and the lands under the water: and when the water fills the pores on all sides through which it could evaporate, it mixes and decocts at the same time what is mixed in the stones; for which reason such places are generative of stones. Moreover, there is a flow of certain waters through very strong mineral powers, and when they flow through such materials, they are imbibed with those minerals; and therefore both the waters and those things immersed in them are converted into stones, more quickly or slowly, according to whether the formative and productive power of the stones is strengthened or weakened.

The reason why water divided near the bank poured from a fountain is converted into stone more quickly than the water flowing from the fountain and river or sea is because that power overcomes a small and divided amount more quickly than a large, undivided one, as is the case in every power converting something; for every such power converts the small more quickly than the large. That the same water poured in some place is not converted into stone happens because, when it is outside the mineral place, it evaporates and corrupts, just as every other thing is corrupted outside the place of its generation. That water receives and is imbued with such a power is proven by other accidents of water, such as the taste of sulfur, arsenic, or bitterness. For water does not contract these tastes except from the places through which it passes.