The herald., 1895-06-09

being of the same class as the atmos'
pheric curve must differ somewhat from
ii, Just as one cone-a certain section OF
which gives the parabola or the hyper
bola-differs from another; and this be-
cause the expansion and compression
shown by the increase or decrease OF the
diameter of the base of the cone while the
altitude remains the same-of solids dlf-
I fers appreciably from that OF gases.
1t is then evident that if we are able TO
construct the curve. even approximately.
1t will show the approximate density OF
every portion of the interior of the earth
and therefore to greater or less extent
its physical condition at each point. II
the curve is then parabolic or hyperbolic
in character, will its vextex ta!l at the
center of the earth? If it does, then the
maximum density point will be exactly
at the earth's center. and the density OF
the earth will increase at "a gradually in
creasing rate from the surface up to the
center, the whole of which seems TO be an
apparently plausible suppositon. But
we can accept or discard this suppostlon
when we determine what would be the
approximate maximum density given by
such curve.
If we knew at what distance below the
surface the earth s surface density became
doubled. we could then construct the
curve approximately, and readily deter
mine the approximate maximum density
at the center given by such curve.
From the value of the maximum density
thus determined we can accept or reject
the speculation on which it is founded; !;
for half OF the sum of the maximum and
the surface density should be nearly
equal to the mean density. In fact it is
possible to arrive at consistent conclu-
siol by exclusion just as the physician
diagnoses an obscure disease.
If the above distance in the earth is as
many times greater than the correspond
ing distance in the atmosphere (3.4 mlles)
as the coefficient of com preston. or of
the correlated or better known coefficienJ
of expansion OF solids is greater than
that of gasses, we can assume this dis
tance to be about 1000 miles; then the
maximum density at the center of the
earth will be nearly 800, if the surface
density is 81. The above maximum dem
sity point is obtained on the ass umption
that the composition of the earth re-
mains constant like that of the atmo-
sphere. But there are very strong doubts
whether the composition OF the earth
remains constant. For if we accept the
nebular origin of the earth, it is very
plausible to suppose that the heavier e'e
ments and their compounds are more
abundant in the interior than on the
surface of the earth. Ii this is so, then
the maximum density as above deter
mined will be more or less largely in
creased.
~ If the density increases regularly from
the surface to the center the maximum
density should be twice the mean density
less hn surface or minimum density.
which is equal to IL. Therefore q maxi
mum density given by curve would
probably not be much over ~. Hence
the maximum density of 30 or more, as
stated above. is altogether too large, and
we must reject the surmise on which it
is founded.
IN inc f0r hn Of hi rnin
tion, 1t is to be noticed that density,
which is shown by the inverse or recipro-
cal ordinates of the curve. increases more
rapidly the nearer it approaches the YER
tex OF the curve. If the density increases
from the surface to the center. the maxi
mum density must be at the center. But
as shown above. the maximum density
thus obtained will be inordinate. 1t is
true that it will be largely reduced by in
creasng the unit OF distance from 1000 to
about 300O With such a curve the in
crease in density for quite q distance