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, 2>d, 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 



