New-York tribune., 1842-03-22


.l.raac,. il,.a the. exist; astF,,,rt3t e9a>'d-
cradle depth the Ilor1s diminish ls!d roc>S be-
come stronger, aud bla % cryStis.tzs. triit ne
reach the bottom. uilc; t.Iey ilase no Poges,CF
t,iEiza,ion has .aNea place y;nder pressure, ana
cney haze $owly cooici. The Putouic tocSs con-
sisi Of certain p0rphyries, and haze sick and aiu-
zinc bur never scor4 orvccanic sand or pebbles.
nor .lisv signs OF these :ou5. near the surface.
~ therefore. Volcanoes md been thus named, be-
cause Vulcan had Ms forge under ftna 50 it
was natural tina; these rocks >hould be called
Plu,onic. a. being found IN me realm, of Pluto,
where flowed the Phlegcrho--rive OF iirc-lnd the
Lethe rolled lis waJerv labyrinth vshca may be
mythical OF The Lethca.l IL luence excrted 81 these
rocks-;or we lind thar whea these granite masses
come in contact with foss.lilerouS strata. they
DESTROY cvcry trace o.: organic remains. II We
suppose al! the different come n contact
with these we shall find ,nas ntrace the pas
sage from those OF the most tossilitcruQ> state 70
that when fossils are rare. ~ last come 20 pure
crystal rock such rs Is sought b; the Sculptor
The Carrara nlarele example OF this kind
Formerly this was called a primitive rock-onc OF
the Oldest Now il IS known not 70 be o: high an
taty but to have been converted from toSslitcrous
rock bv contact with granite. which has deprived
il of ali tS corals. Its nodu!es OF flint nave been
fused and occasionally viii be found CRYSTALS D,
augite against winch the Soul ptor sometimes break
the edge of his chi>eI. give this an iustra-
ton with which you are all acquainted it IL osy
one OF :. thousand ! mghtmcn;ion. Tnus you see
that rocks which are tossili.crou>, when tar from
Pluronc rocks. many become noa-tossiliiereus
when placed for ages t~s!r vicinity.
Twas fors,ery great puzzle tor chemists 10
account FOR the manner in which heat peryadcd the
rocks because they are bad conductors But they
should recollcct that n the interior OF the lnrth
we have to deal not only with masses OF melted
lRattcr. bu; with steam Volcanoes, besides nlin--
raj ::latter. discharge various gaSes-but nine
tentils Of their matter iswatcr. This steam. be-
fore it found sent, n.iaged Intimately with the
pores OF the lava. and forced the sides to olsen
gaze. AnyrpcI> no matter how solid and compact.
when put in contacyvith an immense reservoir OF
this would become porous aud spon=y, under 50
enormous pressure. This may be seen ut Corlntil,
in the Lpari Islands. in Greece. and other places.
Thi, hypothesis must not be conbaed then. By OBJ
icctions founded upon the results of subjecting
rocks to the hcatzot our furnaces; FOR they exist
uncier altogether different conditions the interior
Of the Earth!
may state. that, as these remarks relate to the
most difficult theories OF geology, it is To be
expected that you should at once follow them. As
omitted at the last lecture. will say a few
words Of the origin OF granite rocks. The true
lnsratitied granite is generally believed TO be OF
igneous origin formed by that part Of the volcanic
phenomenon which i far below where the eruption
takes place. In Mount Der. they are believed to
be below the Miocenc. and in tina below the
Post Pliocenc; and so of all antccedcnt periods.
II is impossible though we know more OF the
history OF tttna than OF any other Volcano to form
even an approximate c>timutcot the number of
wears required for the accumulation OF such mass
of volcanic matter There Is no reason suppose
that the ancient Grupton- were more violent than
the modern. The sheets OF lava separated by
beds Of scoria. and brecca in the ancient part OF
the Volcano, do not appear 70 be OF any greater
thickness than those OF the modern There Is
method OF attempting tho computation OF the
NOR. part OF the mountaili--to consider
the minor which alnrn its flank. OF these
there are eighty Of the first magnitude. We cnn-
not from what inow Of these, suppose that
more than ouc-.ourih OF them were produced since
the earliest periods mentioned by Diodorus Sc'l-
lus and Thncydidcs There may haze been more
activity, less violcnt commissions; bur it we
suppose that, IN l. 600 years ali these eighty
cones were produced and il We strip them all
OF We shall still have the grca, colossal mass of
-ttnn remaining bchinJ II would still be one of
OF the lottiest mountains iii Sicily. It's evident.
at all events that. between the formation of ,thc
latest p.r:o, OF the puy de Tartaret and the oldcs,
of .+.tna- the whole OF the older and newer PHO
Gene periods -.1s:aa integvened
Il M NIX. lect7-e XII eI3eavor 10 explain.
iron. he remains q: LIE temple d Scraps. some
al z.ae T-l'ot- .: ~ e:aos:ayal .; M earth.