12- fcCIEXCE IX SHORT CHAPTE11S. 



silicates i.e. the rock matter separate from tlie metallic 

 matter and solidify on the surface as a thin crust, which 

 behaves in a very interesting- and instructive manner. At 

 first a mere skin is formed. This gradually thickens, and as it 

 thickens and cools becomes corrugated into mountain chains 

 and valleys much higher and deeper, in proportion to the whole 

 mass, than the mountain chains and valleys of our planets. 

 After this crust has thickened to a certain extent volcanic 

 action commences. Rifts, dikes, and faults are formed by the 

 shrinkage of the metal below, and streams of lava are ejected. 

 Here and there these lava streams accumulate around their 

 vent and form isolated conical volcanic mountains with decided 

 craters, from which the eruption continues for some time. 

 These volcanoes are relatively far higher than Chimborazo. 

 The magnitude of these actions varies with the quality of the 

 pig-iron. 



The open-hearth finery is now but little used, but probably 

 some are to be seen at work occasionally in the neighborhood 

 of Glasgow, and I am sure that Sir William Thomson will find 

 a visit to one of them very interesting. Failing this, he may 

 easily make an experiment by tapping into agood-sized " cinder 

 bogie" some melted pig-iron from a puddling furnace (taking 

 it just before the iron "comes y> nature''*), and leaving the 

 melted mixture to cool slowly and undisturbed. 



The cinder of the blast furnace, which in like manner floats 

 on the top of the melted pig-iron, resembles still more closely 

 the prevailing rock-matter of the earth, on account of the larger 

 proportion, and the varied compounds, of earth-metals it con- 

 tains. 



For the volcanic phenomena alone he need simply watch 

 what occurs when in the ordinary course of puddling the 

 cinder is run into a large bogie, and the bogie is left to cool 

 standing upright. I need scarcely add that these phenomena 

 strikingly illustrate and confirm Mr. Mallett's theory of earth- 

 quakes, volcanoes, and mountain-formation. 



In merely passing through an iron-making district one may 

 see the results of what I have called the volcanic action, by 

 simply observing the form of those oyster-shaped or cubical 

 blocks of cinder that are heaped in the vicinity of every blast 

 furnace that has been at work for any time. Radial ridges or 

 consolidated miniature lava-streams are visible on the exposed 

 face of nearly if not quite all of these. They were ejected or 

 squeezed up from below while the mass was cooling, when the 



