REPORT ON GEOLOGY. 
367 
the present day, it would be difficult to lay down more clearly 
the fundamental positions which must be necessarily common 
to every theory, attributing geological phenomena in great 
measure to central igneous agency. He attributes the primary 
and fundamental rocks ,—“ id enim potissimum de primh tantuin 
massa, ac terrae basi, accipio,”—to the refrigeration of the crust 
of this volcanic nucleus ;—an assumption which well accords 
with the now almost universally admitted igneous origin of the 
fundamental granite, and with the structure of the primitive 
slates ; for the insensible gradation of these formations ap¬ 
pears to prove that gneiss must have undergone in a greater, 
and mica slate in a less degree the same action, of which the 
maximum intensity produced granite*. The dislocations and 
deranged position of the strata (phenomena for which he cites 
the writings of Steno,) he attributes to the breaking in of the 
vast vaults which the vesicular and cavernous structure assumed 
by masses during their refrigeration from a state of fusion, 
must necessarily have occasioned in the crust thus cooling down 
and consolidated. He assigns the weight of the materials, and 
the eruption of elastic vapours, as the concurrent causes of 
these disruptions;—“ denique vel pondere materiae velerumpente 
spiritu fracta fornice : ” to which we should perhaps add, that 
the oscillations of the surface of the still fluid nucleus may, in¬ 
dependently of any such cavities, have readily shattered into 
fragments the refrigerated portion of the crust; especially as, 
at this early period, it must have been necessarily very thin, 
and resembling chiefly the scoriae floating on a surface of lava 
just beginning to cool. He justly adds, that these disruptions 
of the crust, must, from the disturbances communicated to the 
incumbent waters, have been necessarily attended with diluvial 
action on the largest scale ,—■“ maximae secutae inundationes.” 
When these waters had subsequently, in the intervals of qui¬ 
escence between these convulsions, deposited the materials 
first acquired by their force of attrition, these sediments 
formed, by their consolidation, various stony and earthy strata : 
—“ Nec dubito postea materiam liquidam in superficie telluris 
procurrentem, quiete mox reddita,exramentissubactis ingentem 
materiae vim deposuisse, quorum aliae varias terrae species for- 
marunt, alia in saxa induruere, e quibus strata diversa sibi 
* Whatever theory be entertained as to the origin of these rocks, a gradual 
transition of character from granite to gneiss and mica slate, assuredly exists ; 
and it is foreign to our present purpose to pronounce on the more minute ques¬ 
tion, concerning their origin,—further than to observe, that if we admit the 
igneous origin of granite, this gradation of character appears to indicate a gra¬ 
dation of igneous action on gneiss and mica slate also. 
