MB. E. W. BINNEY ON THE OKIGIN OP IKONBTONEB. 43 



natural drainage of a country, and throw it into the state of 

 marsh or bog. The roots of trees require an abundant supply 

 of oxygen, which is an essential constituent of the sap, and 

 exists in larger proportion than in common air in the spiral 

 vessels. The marshy state of the land formed a barrier to 

 the ingress of air to the soil, and, consequently, to the roots. 

 The leaves that fell, the broken branches which strewed the 

 ground, were placed in favorable conditions to decay. They 

 could not do so by the mere action of the air, which was, to a 

 great extent, precluded, and they, therefore, acted upon the 

 peroxides of iron in the soil, and robbed it of its oxygen, as 

 we know organic matter regularly does. All the iron in the 

 soil was now reduced to protoxide, and a complete barrier to 

 the entrance of oxygen to the roots was effected, for as soon 

 as any was absorbed by the soil, it must have been appro- 

 priated by this lower oxide, which, on the elevation to the 

 peroxide, again yielded it to the dead organic matter." 



As soon as ever the sesquioxide of iron, whether derived 

 direct from volcanic sources, or from the decomposition of 

 pre-existing rocks in which it had been deposited, mingled 

 with the mud at the bottom of the carboniferous sea, in which 

 grew countless sigillariae roots, like the leaves of the water 

 lily, ramifying in all directions, not only would such living 

 vegetables assist to decompose the peroxide of iron, but the 

 dead branches and decaying roots would render further assist- 

 ance, not merely in this way, but by supplying carbonic acid 

 to convert the protoxide into such a carbonate as is now 

 found in our coal measures. 



Many of the argillaceous iron ores occur in detached no- 

 dules, which have frequently portions of vegetable matter, 

 shells, fishes, or some other piece of organic matter in the 

 inside that appears to have extracted the iron from the sur- 

 rounding matrix; some of them are hollow, and contain 

 crystals of carbonate of lime, and the sulphurets of iron, lead. 



