THE EARLIEST PLANTS. 789 



eral to such an extent as to constitute in some places one fourth of the 

 whole ; and, making every allowance for the poorer portions, this band 

 can not contain in all a less vertical thickness of pure graphite than 

 from twenty to thirty feet. In the adjoining township of Lochabor 

 Sir W. E. Logan notices a band from twenty-five to thirty feet thick, 

 reticulated with graphite veins to such an extent as to be rained with 

 profit for the mineral. At another place in the same district a bed of 

 graphite from ten to twelve feet thick, and yielding twenty per cent, 

 of the pure material, is worked. As it appears in the excavation made 

 by the quarrymen, it resembled a bed of coal ; and a block from this 

 bed, about four feet thick, was a prominent object in the Canadian 

 department of the Colonial Exhibition of 1886. When it is considered 

 that graphite occurs in similar abundance at several other horizons, in 

 beds of limestone which have been ascertained by Sir W. E. Logan to 

 have an aggregate thickness of thirty-five hundred feet, it is scarcely 

 an exaggeration to maintain that the quantity of carbon in the Lauren- 

 tian is equal to that in similar areas of the Carboniferous system. 



If we ask more particularly what kinds of plants might be expected 

 to be introduced in such circumstances, we may obtain some informa- 

 tion from the vegetation of the succeeding Palaeozoic age, when such 

 conditions still continued to a modified extent. In this period the 

 club-mosses, ferns, and mare's-tails engrossed the world and grew to 

 sizes and attained degrees of complexity of structure not known in 

 modern times. In the previous Laurentian age something similar may 

 have happened to algoe, to fungi, to lichens, to liverworts, and mosses. 

 The algae may have attained to gigantic dimensions, and may have 

 even ascended out of the water in some of their forms. 



Whether this early Laurentian vegetation was the means of sus- 

 taining any animal life other than marine protozoa, we do not know. 



If we ask to what extent the carbon extracted from the atmosphere 

 and stored up in the earth has been, or is likely to be, useful to man, 

 the answer must be that it is not in a state to enable it to be used as 

 mineral fuel. It has, however, important uses in the arts, though at 

 present the supply seems rather in excess of the demand, and it may 

 well be that there are uses of graphite still undiscovered, and to which 

 it will yet be applied. 



Finally, it is deserving of notice that, if Laurentian graphite indi- 

 cates vegetable life, it indicates this in vast profusion. That incalcu- 

 lable quantities of vegetable matter have been oxidized and have dis- 

 appeared we may believe on the evidence of the vast beds of iron-ore ; 

 and, in regard to that preserved as graphite, it is certain that every 

 inch of that mineral must indicate many feet of crude vegetable 

 matter. 



It is remarkable that, in ascending from the Laurentian, we do not 

 at first appear to advance in evidences of plant-life. The Huronian 

 age, which succeeded the Laurentian, seems to have been a disturbed 



