350 J. LeConte—Formation of the 
since the density of the earth increases toward the center, it is 
almost certain that the conductivity increases also. The effect 
of this would be to diminish the rate of in- 
creasing temperature, which would there- 
ore be correctly represented by a curved 
line C BE, and not the straight line c D. 
Under these conditions the ordinate of 
3000° on the curved line would not b 
reached at 28 miles, but at some point ¢ 
farther down, say 40 miles from surface. 
But having finally reached the temperature 
of 3000°, which we assume as the fusing 
pet of rocks in our furnaces, we would, 
y no means, find the rocks in a state of 
f rock would undoubtedly very 
greatly elevate the fusing point. How much we know not; 
but let us suppose to 3500°. To find the ordinate of 3500° on 
the curve, we must go still deeper to some point ¢’, perhaps 60 
or more miles from the surface. But here again we would fail 
to reach the lower limit of the solid crust, because the fusing 
point is again elevated above 3500° by the still greater pressure. 
And thus the fusing point flies before the increasing temper 
ture; and where in this chase the former would overtake the 
latter, or whether it would ever overtake it at all, would depend 
on the rate of increase in the two cases. We have not at 
present the data to determine these. 
e conclusion from this reasoning is, that the crust 18 Cer 
tainly much thicker than is usually supposed ; so thick, indeed, 
that the focus of voleanoes and earthquakes must be within us 
thickness ; and it even becomes doubtful whether there be any 
general fluid interior at a 
ec. This doubt is entirely confirmed, according to the - 
physicists and mathematicians, by the effect of the sun 4” 
moon on the earth in producing precession and nuiation, on 
producing tides. In all these phenomena the earth, even Unt is 
the most powerful distorting forces, behaves like a perfectly ™ 4 
solid, and not at all like a liquid or a partly liquid body. ~ 
reasoning of Hopkins, based upon the amount of proces 
and nutation, and his conclusion that the solid shell of thi 
earth cannot be less than 1000 miles thick, is well known. ed pe! 
the majority of physicists and mathematicians it 1s regard b 
menods. Seremban doubts have been thrown poe ee it DY 
men of high ability. But Thomson’s argument, drawP "| 
the behavior of ds cacth under the cdegencrathe ininest 
of the sun and moon, is as yet untouched. It seems to ihe 
impregnable. The result of Thomson's reasoning is, that’ 
