The sun., 1881-11-27

caities we arrive at one suggestive deduction.
viz that while there are about III volcanoes on
the great continental lands Of the globe. there
are nearly twice as many upon the islands scat
tered over the various oceans. Upon looking
still more closely into tho situation OF conti-
mental volcanoes we perceive another Interest,"
ing fact. namely. that in almost every case the
vents are either close to the coasts Of the con-
tinent or at no great distance from them. The
apparently anomalous case OF the Than Shan
volcanoes. tho only accounts OF whose erup-
tions arc contained In Chinese histories
and treatses. Is susceptible Of explana-
tion when We call to mind that as late
certainly as pliocene times. great In
land sea spread over the districts
where the Caspian. the Sea OF Aral. and many
other isolated lakes are now found. One other
frequent observation relating to volcanic distrl-
button should bo here noted. 1t has been
shown by Mr.. Darwin that II we trace upon
map the areas Of the earths surface which are
undergoing upheava and subsidence respec-
lively. we ahall find that nearly all the active
volcanoes OF the globe are situated upon rising
areas. and that volcanic phenomena are con-
spicuously absent from those parts OF tho
earths crust which can be proved at the pres
ent day to be undergoing depression This cu-
rious fact used to be accounted for by suppOs-
Ing that the agency Of sea water Is necessary to
volcanic outburets, but that ex plan nation is now
abandoned Prof. Judd demonstrates that tho
proximity OF the ocean to volcanic vents is not
the cause. but the effect. OF subterranean action.
In other words. the con0Guration OF continental
coast lines has bsen to a considerable extent de-
termined BY the distribution OF eruptive energy
beneath the surface Of the globe.
The effect. however. OF volcanoes on geo.
graphical contours docs not illustrate the most
important function which they discharge In
81 - ,txxn
result OF modern researches 10 to prove that tho
manifestations OF eruptivs energy to which tho
habitual volcanic vents merely contribute the
most striking phenomena. play rcparativ0
and not. As has boon too hastily inferred. q de-t
structve part. They counterbalance the slow
but In tho long run most potential, processes OF
denudation which otherwise would long ago
have levelled our existing continents. 1t is to
the silent and imperceptible action Of atmos-
pherio moisture and frost that tho dis
integration OF tho solid rock masses must
be mainly attributed. and the impact Of
noisy cataract and ocean biIlow produces
consequences which are insignificant compared
with those ascribable to the slight and almost
nnnoticed forces OF the atmos phere. 1t Is q
wril-established fact that the dcnuiing ener..
gies over ut work On the earth's surface would
have been com petent to remove tho present
land masses many times over In the vnss
we ara driven to conclude that the su sub,errnncau
activities productive Of uphsa walls have in past
to sab!asDee S, but have e snsirsy @s
for the waste ocens ioned by the incessant disin-
tegrating action Of the atmosphere. We see.
therefore. that volcanoes may not merely ba
regarded as the safety valves Of the cobr. but
can with equal propriety DO pronounced the
1t Is true that ia ncom Densated effect OF cub.
terraneaD energies acting on the earths crust
those which would result from tho unbalanced
operation OF atmoe pheric forces. In our nearesi
seems to be dssiiiuts i OF both atmo. pilers and
water. wo zee & lobe whose Internal activities
cies. Under theso ercImstan oas VIZ and it's sur:
face. as We might expect. to be COMPOSED OF
rocks which seem to be entirely Of iEneons e.
or frost. river or glacier. being OF most protig.
Gus dimensiona rs compared with those thu
earth. while no features at ali resembling val
lsys or plains or alluvial Oats are anywhere to
bo disrerned upon thu lunnr surface. But bJ
ternal forces on our own globe. the conditions
necessary TO animal and ,vecetahls existenca
occasional interruptions Of such conditions,
broduced on the one hand hy hurricanes and
nnS ny STs safely Sy Ss as
insignificant accidents OF what IL upon thS
e yery piece 81 the
nature Of the sarh's intrrtnr2 An annlysis Of
aad OF a Ai
Greenland. and now generally a'imitrd to bo
ct ct voleapic origin. point to the conclusion that
Stances. either quite uncombinaa or simply
allowed with ono another. and that among theso
globe. as We know. Is a Rreat magnet.
and tho remarkable phenomena OF terres-
their explanation IN the fact that netnllio
iron forms SO large portion Of the
crust OF our earth. which is probabiy .! no grcnt
thickness contains an enormous proportion OF
riais which constitute the interior portions ot
our CLONE. The study Uf volcanoes thus Seems
to confirm the view suggested BY astronomera.
that cur earth consisted nj one time Of metal:
lie mass surrounded by vnporous envelope ot
n.talloi'is. and lat the whole Of the latter.
the exception of tho constituents OF tho atmos-
phere and ocean. have gradu ally entered into
the combination with tho metals Of the nucieua
10 form ths existing crust OF the globe.
ligh, on another question. which has long en-
gagged the attention OF Eoolosiets aud astron-
ton OF the earths interior. Assuming that tho
IN nd m or !s In so Is W rscens rs ems
times the hypothesis OF a LIQUID centre beneath
thin, solid crust was almost universally ac..
scionti,ts arc impelled by many wri@hty con-
sid"rations To- reject this the'ry, The condition
sTal ,t tatatllty And i is farher admitet
quirsrs that THIS general STABILITY has
been maintained during the, vast periods
OF things seems irr"concilahle with mo srpuO-
sition that. at no great d-pth from. tie surface
tne WnOe mass OF me EIODs Is IN n HIIi vOnGi-
ton. Again. II all i.ncous products were de-
rived from central reservoir. We might
tairly expect 10 lind n much greater uniformiiy
OF character among those products ihau really
exists. But in some cases naterilis of totally
different composition are elected nj the sumo
time from clos-lv adjoining volcanic districts.
This would point 10 the existence oi lo'al res
ervoirs; whose LIQUID contents ars walled or
from those Of nrghbOring cisterus by tho
intervening solid mass. Whatever. then.
may be the cause OF volcanic action.
enough is known 10 determine that 1t does
not originate in universal mass o hqufed
material situated 1T no great depth from ths
oarth's surface. That our Globo 10 in \ snlii
condition TO great dapth from the surface. and
posslbl quite 10 the centre. is de tu'tjon con-
cerning which there Is now little dou't among
geologists II Is satisfactory to know that as
tremers and physicists have 10y totally different
methods. arrived at = similar conclusion. Ills
very generally admitted that II tha a,.rrn wors
not rigid mass, its behavior under Mo aitrd'-
tive influences OF tina surrounding m-uhers "
the solar system would be very different tu what
is found 10 bs the case. No doubt no
snrth's fern has been shown hy Iln.l.r-
inaticians 70 be exactly that winch would
bs acquired by a globe composed of Yielding
materials rOtat NJ on its axis at the rata
presented by our auet. This fact ha, often
a. .l.fN.