Complete Works, Vol. V

of matter, such as having hardness for a form, just as has been determined in the book Meteorology. Coagulation and the effect of coagulation are species and passions of matter, and not substantial forms. These people, moreover, persuade others of this opinion from the operations of the alchemists, which all seem to be done by roasting heat, and stones and metals are generated by one such effective power: because it is not necessary to have a proper effective power in a nature in which nothing is led to a substantial species due to the lack and defect of the species itself. But an intolerable error follows from these things, namely that every stone is of the same species as every other stone, but they differ according to more and less in that material species. For all of them have accepted coagulation and its effect, hardness, as species according to these people. But that this is false is shown by the diverse virtues and operations of diverse stones, which follow entirely diverse species of stones. Furthermore, stones would have to be in the same species as metals which, by the same generation, have accepted coagulation and hardness for species. Furthermore, if there were no efficient cause of stones except desiccating heat, then every stone would be dissolved by cold moisture, as we proved in the fourth book of Meteorology, which we have not seen to happen. These, therefore, are the opinions stated through error by the Ancients concerning the generative cause of stones.

CHAPTER V.

On the effective cause of stones according to the true opinion, and on its proper instrument.

We, however, gathering the true opinion from all these things, say that the most truly generative cause is the mineral virtue virtus mineralis that forms the stone. For the mineral virtue is a certain common power efficient of both stones and metals, and those things which are the intermediaries between them. And therefore we add that it is the formative power of the stone, so that it may be made proper to the stone: and because we do not have proper names for this power, it is necessary to declare by similarities what that power is. Let us say, therefore, that just as in the seed of an animal, which is the superfluous part of nourishment, the formative power of the animal descends from the seminal vessels, which forms and effects the animal, and is in the seed in that way in which an artist is in the artifact which he makes through art: so also in matter adapted for stones there is a power forming and effecting the stones and producing them to the form of this or that stone. But this can be seen more expressly in the gums which distill from trees: for we see those to be moisture strongly acted upon by the earthy dry, and therefore to be coagulated by cold, which, when they remain in the tree not distilling, the power of the tree generates them into wood, leaves, and fruits. However, by that same mode, it happens that when the matter of the dry acted upon by unctuous moisture, or the matter of the moist acted upon by the earthy dry, is adapted to a stone, and there is generated in it from the power of the stars and the place, as will be shown below, the formative power of the stone, just as the generative power in seed from the testicles when the semen has been attracted to the seminal vessels, and to each matter according to its species a proper power. And this is what Plato said, that celestial virtues are infused according to the merits of the matter, which work the things of nature. But as we showed in the Physics books, every power forming and making something toward the form of a species has a proper instrument
The mineral power productive of stones has a double instrument.

with which it does its works and produces them: therefore this power also, existing in the proper matter of stones, has two instruments according to the diversity of nature. One indeed is the heat that extracts and digests the moist, inducing coagulation to the form of a stone in that which is earthy and has been acted upon by unctuous moisture: and this heat is directed...