THE SOLIDITY OF THE EARTH. 73 



the lighter metals (i.e., those that we call the metals of the 

 earths, because they form the basis of the earth's superficial 

 crust) will rise along with the silicon, etc., to the surface; 

 these and the silicon will oxidize and combine, forming 

 silicates, and with a sufficient supply of carbonic acid, some 

 of them, such as calcium, magnesium, etc., will form car- 

 bonates when the temperature sinks below that of the dis- 

 sociation of such compounds. 



The scoria thus formed will float upon the heavy metals 

 below and protect them from cooling by resisting their 

 radiation; but if in the course of contraction of this crust 

 some fissures are formed reaching to the melted metals 

 below, the pressure of the floating solid will inject the fluid 

 metal upwards into these fissures to a height corresponding 

 to the flotation depth of the solid, and thus form metallic 

 veins permeating the lower strata of the crust. I need 

 scarcely add that this would rudely but fairly represent what 

 we know of the earth. 



But it may be objected that I only describe an imaginary 

 experiment. This is true as regards the whole of the ma- 

 terials united in a single fusion. Nobody has yet produced 

 a complete model with platinum and gold in the centre, and 

 all the other metals arranged in theoretical order with the 

 oxidized, silicated, and carboneted crust outside; but with 

 a limited number of elements this has been done, is being 

 done daily, on a scale of sufficient magnitude to amply re- 

 fute Sir William Thomson's description of a fused earth 

 solidifying from the centre outwards. 



This refutation is to be seen in our blast furnaces, refin- 

 ing furnaces, puddling furnaces, Bessemer ladles, steel 

 melting-pots, cupels, foundry crucibles; in fact, in almost 

 every metallurgical operation down to the simple fusion of 

 lead or solder in a plumber's ladle, with its familiar floating 

 crust of*dross or oxide. 



As an example I will, on account of its simplicity, take 

 the open hearth finery and the refining of pig-iron. Here 

 a metallic mixture of iron, silicon, carbon, sulphur, etc., is 

 simply fused and exposed to the superficial action of atmos- 

 pheric air. What is the result? 



Oxidation of the more oxidizable constituents takes place, 



