264

3. ON THE SPECIFIC GRAVITY OF ROCKS.

It was thought, during the infancy ofgeological science, that the order of suc-cession in rocks was that of their specificgravities . 3 Even Woodward, with all hisexperience, fell into this error. Mr- Hawks-bee exposed it at the Royal Society , bysimply exhibiting the section of a coalmine.

Considered on the great scale, however,this hypothesis is not, perhaps, altogethererroneous. Generally speaking, the primi-tive rocks are of greater specific gravitythan the secondary; and it appears fromthe experiments of Cavendish and Maske-lyne, that the density of the superficialparts of the globe is less than that of itsinterior.

4. ON THE CONSOLIDATION OF ROCKS.

Nothing is more common, among thenewer rocks, than the alternation of

1 Varenius lib. i. cap. 7- propos. 7. Hawksbee’sExperim. p. 317- Luidii Lythophil. p. 110.