684 On the Evidence that the Earth’s Interior 1s Solid. (July, f 
times, if dropped in suddenly, the spheres did not float until they — 
had begun to melt, but this was owing to their having cemented — 
themselves to the bottom of the pot. When dropped in cau- — 
tiously, or suspended by a wire, they sank only for the space of ; 
twenty to twenty-five seconds, and rose to the surface when barely 
red hot.” : 
These experimenters found that liquid cast-iron expands at — 
least 5.62 per cent of its volume in solidifying. A result that — 
they regarded as under the truth, since the maximum density of 
the molten iron seemed to be little if any above the melting . 
point, while they were obliged to use it at a temperature above 
the point of maximum density.’ fe 
Experiments upon the relative volumes, solid and liquid, of 
tin, lead, zinc, bismuth, cadmium, antimony, iron and CORP 
been made by Nies and Winkelmann. These show that tin, 2m 
bismuth, antimony, iron and copper in passing from the figi 
the solid state expand ; that is, if both the solid and liquid a 
sities of the metals are compared when both are at a tempe? 
ture near the melting point, the solid has the less specific oi 
Hence these metals when hot and solid would float on w | 
and pressure, according to Thomson’s law, would i oe 
fusion points, thus they would remain liquid at a lower agi 7 
ture in the earth’s interior than on its surface,’ a fact Er | 
assist in explaining the eruptive origin of some pea * ] 
Further experiments by Messrs. Roberts and a 
bismuth and iron showed that “ iron expands rapidly (as andthe? 
six per cent) in cooling from the liquid to the plastic ppe appears ; 
contracts seven per cent to solidity, whereas bismu £235 
expand in cooling from the liquid to the solid state ab - 
r cent.* er 
Pp rom the above detailed experiments p she": expand i 
; ief portion ae 
rendered quite clear that the chief po rode poth having th 4 
density taken near the melting point. That further 
the rocks, also, there seems but little doubt, although a] 
1Proc. Roy. Soc, Edin., 1879, X, 359-362. 
2 Sitz. Akad. München, 1881, pp. 63-112. 
8 Proc. Bost. Soc. Nat. Hist., 1880, XX, 470-479. 
4 Phil. Mag., 1881 (5), X1, 295-299. 
