178 EARTH. 
caufe of the covjolidation of thofe bodies; but not one of 
them can be liquefied by fire j without undergoing great 
alterations in its constituent parts. If fuch a fiolid is 
c.ompofed of heterogeneous particles, thefe muft firft com¬ 
bine together and with other particles, fo as to become 
homogeneous: they muft alfo be reduced to fuch a ftate, 
as to combine with fire Li the manner which produces 
liquidity: and it is known by experience, that thefe com¬ 
binations are produced by more or lefs alterations in the 
very ingredients of the fubftance ; either by the lofs of 
fonte of thefe ingredients, or by the addition of new ones, 
or by both. From which caufes, the new fiolid afterwards 
produced by cooling, bears hardly any refentblance to the 
fiolid melted, and frequently none at all. Now, fuch is 
the cafe of all our firata, (volcanic produEls excepted;) 
and this, as I have faid before, is an immediate and evi¬ 
dent proof, that they have not been confiolidated by fiufiion. 
I might confine myfelf to that general demonftration ; 
but I will examine fome of the facts you allege for the 
fupport of your hypothefis. You fay, p. 237, “ I fhall 
only mention one fpecimen, which muft appear more de- 
efive ofi the quefiion .... In this fpecimen, pctro-fvUx, py¬ 
rites, and cinnabar, are fo mixed together and cryftallized 
upon each other .... that it is impoffible to conceive any 
one of thofe bodies to have had its fluidity and concretion 
from a caufe which had not affedted the other two.” 
This is, indeed, a decifive fadt, but againfil you: for, if that 
aggregation of various fubftances had been melted, they 
would not have remained as they are ; you may try it. 
You fay alfo, p. 232, “ It may be aflerted, that no filiceous 
body, having the hardn'efs of flint, nor any cryjlallizalion of 
that fubftance, has been formed except by fired’ What 
may be afijerted in that refpedf, is, that no known opera¬ 
tion of fire has ever produced, either flint, or any cryflal- 
iization of that fubftance. Flint, and other hard fubftances 
of that kind, appear to be your great object; therefore 
J (hall confine myfelf to them. You fay, that the ac¬ 
tual form in which flinty mafifes are found, demonftrates 
that they have been introduced among the firata in 'A fluid 
ftate, by injeElion from fome other placed’ and you “ refer 
thofe who would enquire more minutely into the fubjeCt, 
to examine the chalk countries of France and England.” 
Jf you have examined thofe countries with as much at¬ 
tention as I have done, we may fpeak from recollection. 
Snppofe then that we have before us tome of the high 
chalk cliffs along the Thames, or on the fea coaft. We 
fee there a number of firata, as diftintft and regular as the 
lows of cut (tones in buildings. Each of tiiofe firata, 
from the loweft to the higheft, is imerfperfed, in its malfes, 
with flints of all fixes. Thofe, now diftinCt bodies, are 
not in the chalk , as knots in the wood, round which tlie 
fibres are bent; or as nodes in fialaclites, which alfo have 
ratified inflections in the coatings of the dominant fub¬ 
ftance ; they lie in the chalk, as would equal and (imilar 
pieces of the chalk itfelf, v ithout any alteration or dif- 
t-urbance in the chalk round them. Now, fir, was each of 
thofe firata, from the loweft to the uppermoft, injeEled 
while it was forming ? If fo, the melted flint ought to 
have come from the water above ; but this is impofiible. 
Or did the injedion continue from below > But why were 
not fuch injetlions (topped in the lower firata, inltead of 
being fo equally difteminated in them all } Where did 
the chalk retire that was difplaced by thefe new malfes ? 
Where are the traces of their palfage through the chalk ? 
What was the power that foot thole malfes through fuch 
a refilling medium, in which, as in all others, the refin¬ 
ance would have been as the fquares of the velocities; 
Why was that power intermittent r Thele are queftions, 
to which I cannot find any anfwer for you. After this 
external inlpection o i flints difteminated in chalk firata, 
■let us come to fome of their particulars. In breaking 
m.rny of them, we find them hollow, and filled with un- 
'alV,:d chalk: many round pieces have only a Jlintfihcll, 
autVahe infide is chalk. Ilow can it be conceived, that a 
mfiud matter has been thrown up in bubbles through the 
■t '' 
chalk, and filled with it ? Great quantities of marine bo¬ 
dies are found in thofe firata, fome of which (the echini of 
various fpecies) are like cggfihells, both in fiiape and fra¬ 
gility, and they have only one or two very fmall aper¬ 
tures. Thefe fhells are moftly filled with chalk .- but a 
great many, which, by their external appearance and 
their fituaiion in the chalk, are abfolutely limilar to the 
others, are filled with flint. How could you conceive, 
that injeEtions of meltedflint made through the firata have 
met exactly, not only thofe fhells , but their fmall aper¬ 
ture, in whatever fituation it happened to be in the chalk? 
And how could the chalk that was in before, come out by 
the fame fmall hole through which the meltedflint was intro¬ 
duced ? I cannot doubt, that if you had examined, as I 
have done, thefe and a great many other ftriking fafts, 
you would have alfo thought, as I do, that flint is only a 
particular modification of the chalk itfelf. The manner, 
indeed, is unknown; but we know of no particular pro- 
cefs that can produce flint-, and every circumftance be¬ 
longing to its malfes in the chalk , leads to that general 
opinion alone. 
You quote, alfo, as a proof of your hypothefis, fcfflwood, 
found in loofe firata, impregnated with hard fubftances, 
as fpar, pyrites, flint, and agate ; and the refult of your ob- 
fervations on that foffil is, p. 234, “ that however little 
of the wood is left impenetrated, the divifion is always 
diftinft between the injcFled part and that which is not 
penetrated by the fluid flint-.” but, again, how can you 
conceive, that fuch denfe and hot fluid would be injeEled 
into a clofe fubftance compofed of combuflible fibres? I 
have myfelf found in many forts of firata ,• petrified pieces 
of wood of all the forts you deferibe, and of many others; 
and they contradict your hypothefis by every one of their 
various appearances, a few of which I fitall mention. In 
firata of loofe fand, I have found pieces of wood, fo hard, 
as to ftrike fire with Heel, though impregnated only with 
fine concreted fand ; and the fame firata contain alfo con¬ 
cretions of mere fand, in various (hapes, very limilar to 
thofe of flints. In clayey ftrata I have found pieces of wood, 
hardened by a penetration of clay, that was afterwards 
concreted: they are generally involved by a concretion of 
the fame fubftance ; and limilar concretions are found in 
the fame firata, either round other extraneous bodies, or 
in homogeneous malfes, either fiolid, or cracked, and fill¬ 
ed with Jpar. In firata, where precedes of agatizaticn 
have taken place, I have found pieces of wood penetrated 
with agate-, and in one of thele pieces the agatization has 
been fo gradual, that fome cf the fibres may be feraped 
with the nail, and are frill combuflible , though between 
other fibres fixed and hardened by imperceptible agate. 
I did not find any fepaiate malfes of agate in thofe ftrata, 
as feparate malfes.of flint are found in the chalk ones ; but 
all tlie extraneous bodies were either impregnated or 
filled with that fubftance. Many fea-fhells of the ferew 
kind are thus circumftanced : fome are involved by a 
concretion of the furrounding fubftance, fome are loofe 
in it. If thefe fhells are put into an acid, they are dif- 
folved, and a nucleus only remains, which (hews all the 
lhades of agatization. In the wideft revolutions of the 
fihell, where the fubftance of the Jlratum had been firft ad¬ 
mitted, this has remained opaque ; but it is hardened, 
and has a glolfy furface. Farther in, the agate is (till 
mixed with the fubftance of the Jlratum-, but it begins 
to have fome tranfparency ; and in the deepeft and nar¬ 
rowed revolutions, the agate is almoft as tranfparent as 
glafs. Now, if a rnafs of melted agate had been injeEled in 
thofe fhells, the appearance would have been ablolutely 
reverled; tlie opaque part would have been in the bot¬ 
tom of the fhells, where the fand would have been forced ; 
and the pure agate W'ould be in the outward revolutions. 
'You mention, *>. 233, the pudding-flones of England, 
which, you fay, you have not feen in their natural fituation : 
but, fir, this is only a particular phenomenon belonging 
to a numerous clafs, confiding of concretions of large and 
dillinct materials mixed with land, formed in loole firata 
