, 1870-11-13

Ihe question OF the state OF tho easth's tr-
terror has boen reviewed By Professor David
Forbes, In lecture which We find reported in
Ad1hFe- Earthquakes aud volcanoes arc the
tFtt superficial phenomenA which suggest to
AaJono that the eA1th IL not Of ep1id rock 10
The core; nevertheless, with ali the helps Of
eotenee, ne have not yet the data for : thor
ouEhly conclusiya solution Of the problem.
Tho globe haa diameter Of 7.9ta miles, while
the Steatest depth hitherto attained by mans
direct exploration haa moi reached even oue
milo from tho surface. The sedimenta1y
rocks-thofe mAds up Of tbs debris Of older
rock stratified BY tho an.ion of vater-were
fnr long hae supposed to rest On 1 more
ancient foundation OF granite. It has been
moro Eecent!y ehown that no granite rock is
known which does not At sona plAee or other
break through and Alter OF disturb the eedi-
mentxry rocks which lie abovelt; md hence
these latter must have prE-e1lsted o. tho
spot. And the granite which disturbed than
was later In tina. At present tho oldsat
rocks we know OF arc eediuentary, md wo
cannot SAY Of my rock thtt 1t Was the foun-
datiou On which the otheEs were laid. Vol
canoea teach rs that 1t certain depth they
communicate with molten sea, from which
they der1*e their supplies Of minerals. and
that these mfnet1l1 ara similar In chemical
cons!atntioo' no mattsr shat part Of tho
\ gathered that there muss be 4 continuous
molten eea. from tbs fact, which seems to
be confirmed. that the moon his An Influence
| In r1isins tides upon 1t, a. indicated by =
tidal movement in volcanic e,Qptiors and in
earthquakes. The history Of tn1nes has ahosp
I that the Temperature ct the e41th etesd;.y In
creAsss ~ va deeoond. Txo degrees Fahssn-
hedt PEI hundred feet Ia fair estim1ta OF the
average A. nothing ia known to contradict,
It Ia only fair to suppose that the inczeaae u
kept up; and, II 60, ut the depth OF twenty
| hse milea We shall roach point where lIcr
and l2v1 would ha continuously molten,
Pressure may necessitsse : highet heat 10,
krepiug mltt.r In : melted stats; hus, allow.
ins for this, fifty uilea would BE- eufie.en,
thicfuess Of eolid ctust-a veE lnsieniacsui
thicknnsa compared With tbs Waolo d2neta1-
and ~ for the great intafior, tho oonotu aior
But objections have been raised bow cs1
euch thin crust san1in solid, aud not Be
come molted up aud Aheorbed7 This xouli
4 hayo force II tbera wete 1ny MEANS O,
keeptng up heat supply from within. Bu
tho very pIessnce OF crust implies that .ths
earth Ia parting With mora hast than Is Aup
piled from within And tbs cooling. End los
tuE Of heat would 60 On until sufficient cruB
formed to act - nou-couductor Gnd kpli
tna heat within Il Ia urged thst Thin csus
could not sustain such mnu1talo ranges u
the HiMal1yss and Andes. This II less plaus
ible, einoA II IL founded m rnlttakan notlol
1 II to tic 1elatinu thase .moQntsins hoax IL
tho oEust.; II NO reduce tho ea1th to III
seals Of IN urSngs, the highest xnomnsaiua, al,
tntle4, would shoE no E1aAtaf tueou21ftiA
thau The n&tls ptu1p1ea On 1bs ukin.. TakjuR 1,
egS-shsu into couaadszation, II. eeo, fu{tSet
mora; that b its yesy ahape = vary thin xns
1 n1yb1Ie>ao<Aeuss strength IAN 93koacratoa