1821.1 Strictures on Professor Buc/daniTs Inaugural Lecture. 303 
see in areolites which are composed of 
an aggregate Of materials, and feldspar, 
mica, and quartz, may have rushed to¬ 
wards each other with vehement affec¬ 
tion—the iron of the feltspar being 
magnetic, perhaps : and all, I believe, 
which our geologists have called pri¬ 
mitive rocks, are composed of more or 
less of these properties, viz. earth, silex, 
and mica, which may be argil in a pure 
state, and are only softer than gianife, 
as they have less quartz, or silex to 
compact them. 
So in the porphyry rock, found near 
granite, at Redruth, in Cornwall, we see 
the major part was once ferrugenous- 
clay, while perfect crystals of pure 
quartz with both terminations, and no 
elongated limb, float, as it were, 
throughout the mass, being by that 
clay intercepted, and incapable of 
reaching the atmosphere of each others 
attraction. 
Again, in mica slate, the mica pre¬ 
vails so abundantly that its crystals are 
all torn up and decomposed; and the 
earthy matter is so deficient, that sepa¬ 
rate garnets lay loose in the mass, as 
in the mellalites of volcanic tufa at 
Pompeii. 
Gniess also betrays the like effect of 
instantaneous attraction; and green¬ 
stone, and serpentine, having most part 
earth, are weakest in point of solidity, 
the cohesion being less compact on ac¬ 
count of the materials possessing less 
of the silicious humour to unite them. 
The water found hermetically sealed 
in crystals af quartz, also seems to in- 
dicate a hasty formation, otherwise it 
would have been evaporated. 
And that granite is also stratified has 
been ascertained partially, and its stra¬ 
tification may probably resemble that 
ladiated stratification on the sulphur 
balls of chalk pits, or that of wavelliie , 
both of which must have been almost 
instantaneous. 
The transition rocks, among which 
are reckoned Grawacke and Grawacke 
slate, and which had better perhaps 
have been left with the primitive, also 
seem of rapid chemical formation, if 
well considered. 
Proceed we now to limestone ; and 
here we shall see not only regular stra¬ 
tification, which belongs to all crysta- 
lized bodies but that of rhombic-fracture 
in its true crystals. For every mountain 
of limestone that I have seen exposed 
to view in its interior, exhibits on the 
section its crystalline origin, as may he 
seen in the vast quarries on the Avon, 
near Bristol ; where their general forms 
still, after all the destruction the flood 
has brought on their apexes, are exhi¬ 
bited, and all their broken parts, when 
disintegrated by art, resemble precisely 
fractured pieces of the calcareous rhom¬ 
bic-spar, by which they are compacted; 
and the excess of which forms veins, 
or dykes, when given or thrust out at 
their consolidation in the moment of 
crystallizing—so that the infiltrating 
sparry or calcareous humour rushing 
forwards, when it found no earthy body 
to imbibe it, as in the hollows or stcal- 
loivits* which air had formed in the 
mass of *mud, assumed there its native 
form or molecule, and lined them with 
those crystals so constantly appearing 
in cavities ; hut when they only found 
a fissure, if the calcareous crystalline 
matter was abundant, they united from 
each of its sides, and fitting closely to 
each other by those laws that gave them 
a decided form, they then composed a 
sort of solid alabaster. 
These veins or dykes of calcareous 
liquid matter* were probably transfixed, 
like ice on the northern ocean, or alu¬ 
minous crystals on cooling. And if 
we find some limestone in which it is 
difficult to . discover the rhomboidal 
fracture or particles, it is, I apprehend, 
because they are loaded with aggregates 
of shells, corals, and zoophytes, which 
interrupt the lines and portions into 
which they would otherwise divide 
themselves, and which we may witness 
even in clear calcareous spar, when it 
has been obliged by its own law of de¬ 
position, to surround feathered strontian 
or other radiating bodies. 
As remarkable an effect is also seen 
in quartz crystals, infiltrated through 
ocherous clay, whose superabundance 
when liberated from the porous body 
would have formed the usual beautiful 
groups, had they not been entangled in 
the amorphous or spiculous surface of 
the clays or marls, through which they 
distilled, and in its desiccation were 
impressed from; which proves in both 
instances, that strontian was formed 
and crystallized before the arrival of 
the quartz or calcareous spar, as speci¬ 
mens which I possess, will evince, no 
less than the spicula of iron or manga¬ 
nese so frequently found in them. 
Tims to all these beds of limestone, 
made up as we see, of coarse earthy 
* So called from their receiving the 
drainings of limestone hills, during sum¬ 
mer, and overflowing in winter. 
matter, 
