T.IK lOUNDATICNS OF THK CONTINENTS 93 



a.>d sometimes ten to tuclve feet thick. ' The 

 "ccurrcce of this large amount of carbon warrants 

 "S m supposing that it represents a vast vegetable 

 iirowth, either on the land or in the sea, or both 



In hke manner, in later geological periods, beds 

 of .ron ore are generally accumulated as a conse- 

 quence of the solvent action of acids produced by 

 vegetable decay, as in the clay ironstones of the 

 coal formation and the bog iron ores of later times. 

 Thus the beds of magnetic iron occurring in the 

 Lpper Laurentian may be taken as evidences, not 

 of vegetable accumulation, but of vegetable decay 



May not also the great quantity of calcium phos- 

 phate mined in the Grenvillc series in Canada. 

 md,cate. as similar accumulations do in later forma- 

 t.ons, the presence of organisms having skeletons 

 ot bone earth? 



With reference to the carbon and iron ore of 

 the Grenv.lle serie.s, I may quote the following from 

 a paper published in the >„.«./ ,/ ,;, ^ 

 Society of London in i8;o:— 



"The quantity of graphite in the Upper Lauren- 



■an senes ,s enormous. In a recent visit to the 



townsh,p of Buckingham, on the Ottawa River , 



e.^amn,ed a band of limestone believed to be' a 



