GEOLOGY. 229 



maintain that the quantity of carbon in the Laurentian is equal to 

 that in similar areas of the Carboniferous systems." 



After describing the mode of occurrence and discussing the 

 probable vegetable origin of the graphite, Dr. Dawson concludes 

 as follows : 



" We may sum up these facts and considerations in the follow- 

 ing statements : First, that somewhat obscure traces of organic 

 structure can be detected in the Laurentian graphite ; secondly, 

 that the general arrangement and microscopic structure of tne 

 substance corresponds with that of the carbonaceous and bitumi- 

 nous matters in marine formations of more modern date ; thirdly, 

 that if the Laurentian graphite has been derived from vegetable 

 matter, it has only undergone a metamorphosis similar in kind to 

 that which organic matter in metamorphosed sediment of later 

 age has experienced ; fourthly, that the association of the graphite 

 matter with organic limestone, beds of iron ore, and metallic sul- 

 phides, greatly strengthens the probability of its vegetable origin; 

 fifthl}', that when we consider the immense thickness and extent 

 of the Eozoonal and graphite limestones and iron ore deposits of 

 the Laurentian, if we admit the organic origin of the limestone 

 and graphite, we must be prepared to believe that the life of that 

 early period, though it may have existed under low forms, was 

 most copiously developed, and that it equalled, perhaps surpassed, 

 in its results, in the way of geological accumulation, that of any 

 subsequent period. 



" In conclusion, this subject opens up several interesting fields 

 of chemical, physiological, and geological inquiry. One of these 

 relates to the conclusions stated by Dr. Hunt as to the probable 

 existence of a large amount of carbonic acid in the Laurentian 

 atmosphere, and of much carbonate of lime in the seas of that 

 period, and the possible relation to the abundance of certain low 

 forms of plants and animals. Another is the comparison, already 

 instituted by Professor" Huxley and Dr. Carpenter, between the 

 conditions of the Laurentian and those of the deeper parts of the 

 modern ocean. Another is the possible occurrence of other forms 

 of animal life than Eozoon and Annelids, which I have stated, in 

 my paper of 1864, after extensive microscopic study of the Lau- 

 rentian limestone, to be indicated by the occurrence of calcareous 

 fragments, differing in structure from Eozoon, but at present of 

 unknown nature. Another is the effort to bridge over, by further 

 discoveries similar to that of the Eozoon bavaricum of Giimbel, the 

 gap now existing between the life of the Lower Laurentian and 

 that of the Primordial Silurian or Cambrian period. It is scarcely 

 too much to say that these inquiries open up a new world of 

 thought and investigation, and hold out the hope of bringing us 

 into the presence of the actual origin of organic life on our planet, 

 though this may perhaps be found to have been Prelaurentian. 

 I would here take the opportunity of stating that in proposing the 

 name Eozoon for the first fossil of the Laurentian, and in suggest- 

 ing for the period the name " Eozoic," I have by no means 

 desired to exclude the possibility of forms of life which may have 

 been precursors of what is now to us the dawn of organic exist- 



