1884.] On the Evidence that the Earth's Interior is Solid. 683 
Sir William Thomson in 1878 again took up the discussion of 
the earth’s solidity, based on the assumed greater density of the 
solid than liquid rock. He seems at that time to have only been 
aware of Bischof’s experiments, but in a note subsequently added 
by him, Whitley’s experiments appear to be accepted as decisive 
against his views, Starting with the, to him, probable supposition 
that the solidified crust of the earth would sink towards the cen- 
ter, Thomson says: “ As soon as the surface began to freeze, and 
to freeze in sufficient quantity not to be floated up by mere super- 
ficial solidified foam, the mass of rock would fall down towards 
the center. More would then solidify at the surface. This also 
would fall down, and the same thing would go on again and 
again. Gradually a sort of honey-combed solid would be formed. 
By-and-bye [sic] a skeleton or frame-work through the whole 
would mount up to an extent sufficient to build up piers, as it 
were, to the surface, and the spaces between these piers, when 
close enough, would, in the continued freezing of the lava, be 
bridged across by solid rock thick enough in proportion to- 
breadth not to break down and sink. There would, again, be 
breaking away of the piers and upheavals of the liquid material 
below; but by degrees the honey-combed mass would become 
nearly like a solid throughout with comparatively small inter- 
ices of liquid lava. * * * The conclusion to be drawn 
‘sspecting the internal condition of the earth is, that we are not 
to infer liquidity of the interior, even if we should find evidence 
of a much higher internal temperature than that which would 
melt the rocks under ordinary pressure.” 
The interior heat, Thomson states, “may be 4000° F., or 
300°. It may possibly be 8000° or 10,000°.” 
In 1879 investigations were made by Messrs. J. B. Hannay and 
: Anderson on the expansion of cast-iron when solidifying. 
The chief method used was the flotation of a sphere of cast iron 
molten bath of the same. The latter was cooled near to the 
ng point afd then the solid spheres dropped in. “They 
found to sink at once when dropped in cold, and they 
ee under the metal till they had acquired a temperature 
. “PProaching visible red; but at that temperature they rose to 
_ ;. face, and as they gained more and more heat from the 
uid metal, their line of flotation rose higher and higher. Some- 
ina 
Were 
: i; 
| Tans. Geo 
. l. Soc, Glasgow, 1878, vi, 38-49. 
