THE OLD RED SANDSTONE. 237 
and from one combination to another, constitutes surely a 
highly interesting subject of inquiry. The transmission of 
iron in a chemical form, through chalybeate springs, from 
deposits in which it had been diffused in a form merely me- 
chanical, is of itself curious; but how much more so its pas- 
sage and subsequent accumulation, as in bog-iron and the 
iron of the Coal Measures, through the agency of vegetation ! 
How strange, if the steel axe of the woodman should have 
once formed part of an ancient forest ! — if, after first exist- 
ing asa solid mass in a primary rock, it should next have 
come to be diffused as a red pigment in a transition conglom- 
erate — then as a brown oxide in a chalybeate spring — then 
as a yellowish 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 Meas- 
ures—then as a layer of indurated bands and nodules of 
brown ore, underlying 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 trans- 
migrations which have passed, and the changes which are yet 
to come. Crystals of galena sometimes occur in the nodu- 
lar limestones of the Old Red Sandstone; but I am afraid 
the chemist would find it difficult to fix their probable 
genealogy. 
In at least one respect, every geological history must of 
necessity be unsatisfactory ; and, ere I pass to the history of 
the two upper formations of the system, the reader must per- 
mit me to remind him of it. There have been individuals, it 
has been said, who, though they could see clearly the forms 
of objects wanted, through some strange organic defect, the 
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