872 



THE WONDERS OF GEOLOGY. Lect. VIII 



deposits in which that metal was mechanically diffused ; 

 and the formation of bog-iron, and of iron-stone, through 

 the agency of vegetable matter {ante, p. 739), are familiar 

 examples of these changes, and have suggested to Mr. Hugh 

 Miller one of his happiest illustrations. " 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 (ante, p. 757) 

 — then as a brown oxide in a chalybeate spring — then as a 

 yellow ochre in a secondary sandstone — then as a component 

 part in the stems and twigs of a thick forest of arboraceous 

 plants — then again as an iron carbonate slowly accumulating 

 at the bottom of a morass of the Coal-Measures — then as a 

 layer of indurated bands and nodules of brown ore, under- 

 lying a seam of coal — and then, finally, that it should have 

 been dug out, and smelted, and fashioned, and employed for 

 the purpose of handicraft, and yet occupy, even at this stage, 

 merely a middle place between the transmigrations which 

 have passed and the changes which are yet to come !"* 



36. Review of the Hypogene rocks. — Enough has 

 been advanced to convey a general idea of the characters 

 and relations of the primary rocks, and of the changes 

 induced on contiguous sedimentary deposits by their influ- 

 ence, when injected or upheaved in an incandescent state. 



The traces of stratification — a structure which we have 

 seen is characteristic of aqueous deposition — are evident 

 in the uppermost metamorphic rocks ; and there is also a 

 distant analogy to the alternate depositions of secondary 

 beds, in the succession of different mineral masses, as gneiss, 

 mica-schist, quartz rock, &c. But in the lowermost term 

 of the series, the granite, even these apparent relations to 

 the stratified formations are altogether wanting : and in the 

 amorphous masses, veins, and dikes, we see the effects of 

 * The Old Red-sandstone, p. 250. 



