DAWSON—LAURENTIAN GRAPHITE. 117 
marine formations of more modern date; thirdly, that if the Lau- 
rentian 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 graphitic matter with organic 
limestone, beds of iron ore, and metallic sulphides greatly strengthens 
the probability of its vegetable origin; fifthly, that when we con- 
sider the immense thickness and extent of the Kozoonal and graphitic 
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 of this 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 
Hozoon and Annelids, which I have stated in my paper of 1864, 
after extensive microscopic study of the Laurentian limestones, to be 
indicated by the occurrence of calcareous fragments, differing in 
structure from Lozoon, but at present of unknown nature. Another 
is the effort to bridge over, by further discoveries similar to that of 
the Hozoon 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 Zozoon for the first fossil of the Laurentian, 
and in suggesting 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 
existence. Should remains of still older organisms be found in those 
rocks now known to us only by pebbles in the Laurentian, these 
names will at least serve to mark an important stage in geological 
investigation. 
