310

NATI!UAL rJIlLOSOPHV.

period, respecting these substances, were exceedingly in-correct. The doctrine of equivocal generation which hadbeen adopted by the disciples of Aristotle , contributed verymuch to mislead those who made these substances the sub-ject of their inquiries; since by also adopting the aid ofcertain occult qualities, their origin was supposed to employtheir influence in the earth, in creating substances whichbore the figure and resemblance of various vegetable andanimal substances. To account for their formation, there-fore, it was thought sufficient to refer to the hidden powersof the vis plaslica, the vis formativa, and the vis lapidifica-tiva.

“ In the sixteenth century, the workmen employed in re-building the citadel of Saint Felix at Verona, discoveredthat the rock on which it was built was full of petrifiedshells. This discovery excited the attention of the learnedto a very considerable degree; some attributing them to theactive influence of the vis formativa; whilst others, per-ceiving their exact resemblance to real shells, declared theymust be actual marine bodies thus enveloped in stone bvsome accident. We learn, that when Fracastorius wasasked his opinion respecting the phacnomenon, he made foranswer, that it had been attempted to be accounted for inthree different w'avs. Some attributed it to the vis plaslicaand formativa of Aristotle ; others supposed these substancesto have been real marine bodies deposited in these places atthe general deluge; whilst others adopted that opinion tow'hich he himself was most inclined, that those parts wherethese marine bodies were found, had formerly been coveredwith the sea, which gaining insensibly on some parts of dryland, gradually changed its bed, leaving the positions it hadformerly occupied for the cultivation and possession ofman. ,+

“ In the sixteenth century, Agricola, to whose indefatiga-ble spirit of inquiry mineralogy is very much indebted,spoke more explicitly of extraneous fossils than had beenhitherto done. He particularly mentions the entrochi, andrelates several instances of trees, and parts of trees, beingfound in a petrified state at considerable depths in theearth . 15 But, it is evident, that Agricola was not partial toinquiries respecting extraneous fossils; his attention waschiefly engaged in mineralogy, to the promotion of whichhis industry added very considerably.

“ *♦ Bonani Museum Kircherianum, p. 198. Museum Calceolarii et MuseumCom. Moscardi, p. 172.

’s De Ortu et Causis Subterr. lib jii.; et De Natura Fossil, lib. rii.