130 Proceedings of the Royal Physical Society. 
descend into the interior of the crust of the earth, as affording 
evidence that there was a " Central Heat/' The increase in 
temperature is such, that at no great distance all matter 
must be in a highly ignited state ; and, according to some 
physicists, a large part of the nucleus of the earth may be in 
a white hot, and fluid state ; whilst in the centre the matter 
may be in a highly rarefied and vaporised condition. The 
ordinary theory of accounting for the cold surface and the 
heated interior, is to assume that the solid film or crust rests 
on molten matter; but such a supposition is unlikely, as a film 
of solid water or ice cannot rest on hot water without becom- 
ing liquefied, and no more can a film of solid granite or mineral 
matter rest on a molten mass of the same material. The 
theory originally suggested by Dr Macadam, and explained to 
the Society, called into force the spheroidal state of matter. 
Water thrown into a highly heated vessel does not readily 
pass off into steam ; in fact, the water does not touch the 
vessel, but rolls itself up into a spheroid, which remains at 
some distance from the highly heated vessel, and very slowly 
passes into vapour. Again, if a heated rod be plunged into 
water, the latter is repelled by the spheroidal force, and 
until the heated rod becomes reduced in temperature, there 
is scarcely any disengagement of steam ; but whenever the 
rod becomes cooled down, then the water touches it, and 
passes off in steam. These experiments on the spheroidal 
condition of water when influenced by heated metal, Dr 
Macadam brought to bear on the central heat of the earth ; 
and he assumes that our globe internally consists of three 
distinct portions, viz., 1st, A central nucleus in a highly 
ignited state ; 2d, A space enveloping and surrounding this 
heated nucleus ; and, 3c?, A crust at a comparatively low 
temperature, the inner side of which is in the spheroidal 
state. The above arrangement is similar to that observed 
in an ordinary egg. The yolk of the egg represents the 
mass of matter in a state of igneous fusion ; the white of 
the egg occupies the position of the space between the 
heated mass and the crust ; and the shell of the egg corre- 
sponds to the outer crust of the globe. The outer film or 
solid crust of the globe will thus be influenced by two great 
