236 THE POPULAR SCIENCE MONTHLY. 



in their remains of j^lant-life, are no less trust-svorthy proofs of its 

 existence. They are themselves largely the result of vegetation in 

 some form. Dr. Hunt originally explained this connection, illustrating 

 it by identical processes in the world about us. If the reader visits a 

 bog-land in summer, where slowly-running or stagnant water collects 

 in pools, or if he stands upon the edge of a morass or marsh, he will 

 notice angular, iridescent films floating upon the surface. They are 

 thin pellicles of iron oxide, which will soon break up and sink, to be 

 succeeded by fresh "skins," which in turn disappear, building up a 

 growing layer of bog-iron ore beneath the water. The theory is simple. 

 Iron exists under two forms, a soluble or monoxide, and an insoluble or 

 sesquioxide. The latter is widely disseminated through the rocks and 

 soils. The insoluble modification is reduced to the monoxide or sol- 

 uble state in the presence of finely divided and rotting vegetable 

 matter, or in water charged with vegetable infusions, as emacerated 

 leaves and tissues. Rains and streams carry it away to lowlands and 

 depressions, where it becomes, through contact with the air, again oxi- 

 dized or rendered insoluble, and is redeposited in streaks and bands. 

 The widespread action of vegetable acids is here concerned. Humic, 

 crenic, apocrenic, and related acids, in conjunction with the reducing 

 power of carbonaceous residues, removed iron oxide from the original 

 rocks, and through the agency of water gathered it useless as long as 

 it remained scattered in minute particles through vast terrains into 

 enormous masses, the source and maintenance of our industries, thus 

 garnered through these gentle and silent methods. Such has been the 

 growth of the large deposits in the Marquette region, in the Adiron- 

 dacks, and at Pilot Knob deposits which under the influence of heat 

 have become changed into the specular ores, the magnetites, and hema- 

 tites. They point unmistakably to the existence of plants, and no less 

 to their duration over immense periods of years. 



The proofs of animal life are less satisfactory, and have been dis- 

 credited in high scientific writings, or, more accurately, the morpho- 

 logical types of that life have been rejected, leaving the general pre- 

 sumption unquestioned that animal life of some kind prevailed. In 

 the first place, the phosphatic minerals found in the archgean rocks are 

 considered derivative from organic remains, as to-day phosphorus as a 

 phosphate results from animal secretions, though phosphorus is omni- 

 present in the plant-world, and the ashes of various vegetables yield 

 from eight per cent, to fifty-three per cent, of ^^hosphoric acid, while 

 the annual shipment of flour and wheat from our shores represents 

 thousands of tons of this element. In this respect the evidence does 

 not seem altogether controlling that these archgean phosphates neces- 

 sarily resulted from animal debris. But the argument rests upon surer 

 grounds. In 18G5, Logan, Dawson, Carpenter, and Hunt, ^^repared a 

 paper of great merit u])on an archa^an fossil, which they named Eozoon^ 

 and whicl] they considered representative of the zoological sub-king- 



