INTERNAL CONDITION OF THE EARTH. 305 



test his results, but on a far larger scale, and 

 extend the investigation to many materials besides 

 those which he used. 



In the meantime, the only experimental evidence 

 we have, being Bischoff's, is to the effect that 

 the melted rock is of less specific gravity than 

 the solid rock, and that the solid rock would 

 therefore sink clown when frozen. Without in- 

 sisting on this as being proved, I shall just call 

 your attention to what would be the probable 

 history of the solidification of a molten globe if 

 this were the case. As soon as the surface began 

 to freeze, and to freeze in sufficient quantity 

 not to be floated up by mere superficial solidified 

 foam, the mass of rock would fall down towards the 

 centre. 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 

 honeycombed solid would be formed. By and by 

 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 con- 



VOL. II. X 



