454 



HISTORICAL GEOLOGY. 



has converted the carbon into graphite. The little-altered Huronian beds 

 of Wisconsin still contain much carbonaceous material, as remarked by 

 Brooks and Chamberlin. The former stated, in 1876, that "the considerable 

 amount of carbon distributed through the Huronian indicated much organic 

 life, and leads to the hope that " those imperfect f ucoidal impressions 

 reported by Julien, in the second volume of the Report on the Geology 

 of Michigan, may not prove delusive. 



The earliest plants were, beyond doubt, Algae, water species, which grow, 

 like most plants, by taking carbon from carbonic acid ; and after these, the 

 microscopic Fungi related to the Bacteria (Microbes), which take their car- 

 bon for growth chiefly from organic products ; for these minute plants are 

 essential to the process of decay of organic matters and also to the produc- 

 tion of many mineral changes, as already explained. 



The chert of the limestone in the Penokee belt of Huronian, and the 

 jasper associated with the iron ore of the belt, consist partly of opal-silica, 

 and are probably from silica-secreting Algae (Irving, Van Hise). It is proba- 

 ble that plants related to those that are now secreting limestone and silica 

 in the hot waters of Yellowstone Park, below temperatures of 185°, were 

 already doing geological work in the making of limestones and silica deposits 

 during the later Archaean. One species of supposed "seaweed" has been 

 named Archceophyton Newherrianwrn by N". L. Britton, The specimen, from 

 a New Jersey crystalline limestone, consists of graphite arranged in narrow 



parallel stripes, with a regularity that suggests 

 organic origin ; but the arrangement may well 

 be an effect of the pressure attending metamor- 

 phism. 



Animals. — With regard to animal life, the 

 supposed fossil, Eozoon Canadense of Dawson, is 

 regarded by some as proof of the existence of Rhiz- 

 opods (Foraminifers), while others believe it to be 

 of mineral origin. It occurs in coral-like masses 

 which are sometimes several feet in diameter. 

 Fig. 503 represents, natural size, a section of a 

 specimen from Grenville, Canada. The white 

 bands are the calcareous layers supposed to have 

 been secreted by a layer of the Rhizopods, while 

 the dark bands correspond in position to the layer 

 of Rhizopods, and are made up of mineral mate- 

 rial (serpentine generally, sometimes pyroxene, loganite, etc.) that, after the 

 death of the animals, filled the cells. Dilute muriatic acid removes the lime- 

 stone, and opens the rest to examination. 



503. 





Eozoou Canadense. Dawson. 



Localities occur in the third or Grenville stratum of limestone near Grenville, and in 

 the Petite Nation Seignory ; also in Burgess (where the calcareous part is dolomite), and 

 at the Grand Calumet, in a limestone whose place in the series is not determined ; and at 

 Tudor in Hastings County. Eozoon has also been reported from Archaean rocks in Bavaria 



