52 
REPORT—1847. 
For in 
proper- 
perature of thft interior of the globe to be due to its original heat, 
such case the increase of temperature in descending must be nearly 
tional to the depth (as it is observed to be near the surface), so long as tbe 
ratio which the depth bears to the earth’s radius is sufficiently small; and tbe 
rate of increase detemiined by observation is such that the temperature at 
depths much less than the thicknetis of the solid shell according to thereeults 
above obtained, would probably be far greater thaa the tctnjjcrature of fu* 
sion for the matter forming the crust of tlic globe, uniler the ordinary atni^ 
spheric pressure. In other words, the thickness of the solid crust would, in 
such case, be very small instead of being large, os it must be accordliig M 
our previous determination. Allowing then the correctness of that ilctw- 
raination, and supposing that it should be hereafter determined by experiment 
that high pressure has no appreciable elfcr-t in increasing the temperature of 
fusion, we must necessarily conclude that the existing terrestrial temperatnre 
cannot be due to the oartli’s original heat. But let us suppose that pressure 
does affect the tcnijierature of fusion ; then as the depth Increases wr sliail 
have with the increased tendency of heat to prevent .solidification, an increased 
tendency of pressure to promote it. by rendering the mass fusible only ot i 
higher temperature, and it is maiiifesl, that If the latter tendency £dwfl« 
increase as rapidly as the former, the earth must be solid at all depths 
well as at the surface. 'W’c may consider the terrestrial temperature foit- 
crease by 1® Falir. for 60 or 70 leet of depth; and in order that the tendency 
of pressure to jiromotc solidification may increase at the same rate, tlte tem¬ 
perature of fusion for tho terrestrial matter must increase by 1® for an inerrase 
of pressure on a square foot of surface, equal to the weight of a colump of 
which the length is 60 or 70 feet, and the transverse section one square foot. 
It then the temperaturo of fusion for the matter constituting the globe 
should bo found to increase by pressure at the rate of 1® Fahr. for an increase 
ot pressure equivalent to that of about five atmospheres, w'c might conclude 
tliat the earlh must be solid at least to those depths to which the terrestrial 
temperature may increafui accowling to the law observed near to the surface. 
It the temperature of fusion increase nt a more miiid rate than hercstated 
with the increase ot pressure, the above conniusion will d/ortion be true: 
•■apid.^re should probably have the condition 
under which solidification would eommeuce at the centre. In this cast'- 
tiin ^ surface, the earth would consist of a solid 
SuLd'fm d 'vith fluid matter between them, as already 
Sion and I, *''‘‘“1^ bo com[ilnti.. Tlin nroWtro of pi«» 
Ttml ‘ boon iolvod. It i a more wn.# 
sfcoLTln t notyk-ld to the artiliM 
of mtIo il,«,r. 1 ‘b® “"'■■“I midcus i, Huiri. Tl.i.ho.revrr« 
oL-TvetiX S ino’™ ™“ r"; bore nsi,um«i, and «tli 
than ill tlie more fjecomes here still more appwec/ 
of our subject fart ^ "I'ich I haveentored on this branc • 
ment. it isCbab ; ,nn.;./! 1 1" bo detected at all by exj^n- 
to justify the cmicLsioii ofTh ^ *j|3n that stated above as 
could, l^conceivG, in s„,.h Lm- b/l ttiVif 
If, on the eontrn^ iV !i . 11 ^ ‘o the earth’s entire solv 
fiiienco, or that it lends^tn t- that pressure exerts no suciii«' 
Hall’s expewimLu wu mn ♦ ‘i L in the case, of Sir Jamr^ 
» must conclude, as above sUted, that the interior tern* 
