The Scottish Naturalist. 171 



into the sea. This simple re-arrangement of the primary rocks- 

 is a perfect illustration of what is now taking place, in so far as. 

 re-arrangement is concerned, and yet the sources of the redis- 

 tributed materials are indeed almost endless. 



But we will follow out the decomposition of granite some- 

 what farther, and we may, perhaps, see more clearly what the 

 laws which govern distribution and chemical combination have 

 produced from these rocks. From quartz, silica is derived; 

 from silica, silicon ; from mica, magnesia, lime, potash, peroxide 

 of iron, silica, &c. ; from magnesia, magnesium ; lime, calcium - r 

 potash, potassium ; from peroxide of iron, iron ; from felspar, 

 silica, alumina, and potash ; from alumina, aluminium ; and so 

 on ; and from the ultimate division of all these, oxygen. 



From quartz, as has been said, all sandstones were derived 

 (in a former paper on " Trap Rocks," see Scottish Naturalist,. 

 Vol. II., p. 219). Silex was more particularly spoken of, but 

 (where magnesia is named as a colouring material please read 

 manganese) it is not soluble in water at its ordinary temperature, 

 but it is contained in the waters of the Geysers, and some 

 thermal springs, and if fused with an alkali is soluble in water,, 

 but much of its operation and modification in nature is beyond 

 present chemical knowledge. 



To the lime and magnesia of mica (and to trap rocks, &c.) are 

 owing the immense accumulations of lime, mountain limestone, 

 magnesian limestone, chalk, &c, and to the peroxide of iron of 

 mica, many of the iron impregnated masses of the earth are 

 due. 



Clay, with its alum and potash, under any circumstances 

 whatever found has possibly come from the felspathic ingredients 

 of the early rocks. 



Lime is a compound of calcium, carbon, and oxygen ; but to 

 attempt to follow these substances through their wonderful 

 metamorphoses and combinations would be as absurd as it 

 would be endless. The following graphic description of the 

 important part that iron is playing in the economy of things 

 tnay show us what a work this would be : — " How strange, if 

 the steel axe of the woodman should have once formed part of 

 an ancient forest ; if, after first existing as a solid mass in a 

 primary rock, it should next have come to be diffused as a red 

 pigment in a transition conglomerate ; then as a brown oxide 

 in a chalybeate spring ; then as a yellowish ochre in a second- 

 ary sandstone ; then as a component part in the stems and 



