182 



PALEOZOIC TIME. 



there is wanting, therefore, all evidence of a diversity of climate and 

 of oceanic temperature over the earth's surface. With a warm and 

 equable climate, the atmosphere would have been moist and the skies 

 much clouded ; but storms would have been less frequent or violent 

 than now. The eyes of the Trilobite, as Buckland observes, indicate 

 that there was the full light of day, and therefore that sunshine alter- 

 nated with the clouds as now. 



So far as has been deciphered in the history of the Primordial 

 period, there was no green herbage over the exposed hills; and no 

 sounds were in the air save those of lifeless nature, — the moving 

 waters, the tempest and the earthquake. 



8. Exterminations of life. — The life of the Primordial period 

 changed much during its course ; and, at one time — the close of the 

 Acadian epoch — there was a general extermination of the species 

 about the eastern portion of the continent ; for no species of this epoch 

 have yet been found in the higher rocks. Among the Trilobites, the 

 genus Paradoxides, some of whose species were the largest of known 

 Crustaceans, became extinct ; most of the other genera remained, but 

 were represented by new species. No Trilobites of the Primordial 

 extend up, so far as known, into the beds of the next period. 



V. Disturbances during the progress of the Primordial period. 



In Newfoundland, the beds of the Potsdam division lie unconform- 

 ably over those of the Acadian, indicating an epoch of disturbance 

 between. No direct evidence of a similar disturbance over the rest of 

 North America has yet been made known, beyond the fact of the de- 

 struction of the Acadian life above mentioned, and the additional 

 observation, by F. H. Bradley? that at Henry's Lake, Idaho, a quartz- 

 yte (probably Potsdam) underlies unconformably the beds of the 

 Quebec group. The fact, stated by Emmons, that pebbles of the Pots- 

 dam sandstone are included in a conglomerate at the base of the Cal- 

 ciferous, seems to show that the consolidation of the Potsdam had 

 taken place before the Calciferous era. 



2. CANADIAN PERIOD. 



1. American. 



Epochs. — 1. The Calciferous, or that of the Calciferous sand- 

 stone of New York, etc. 2. The Quebec, or that of the Quebec 

 group in Canada. 3. The Chazy, or that of the Chazy limestone. 



I. Rocks: their kinds and distribution. 



The area over which the rocks of the Canadian period are the sur- 

 face rocks follows nearly the border of the Archaean in Northern New 



