ANNIVERSARY ADDRESS OP THE PRESIDENT. 



53 



matter of the Laurentian rocks was laid down or accumulated in 

 beds like coal is improbable, no evidence whatever tending to show 

 that there existed terrestrial vegetation. On the other hand, the 

 hydrocarbon may have been due to diffused bituminous matter 

 closely resembling " our bituminous shales and bituminous and oil- 

 bearing limestones." Research hitherto has failed to find traces of 

 any organism save the Eozoon ; no cryptogam has yet occurred ; and 

 we cannot imagine that, if of vegetable origin, the organic matter 

 could have been so completely disintegrated and bituminized prior 

 to being changed into graphite. Dr. S. Hunt believes he has de- 

 termined the presence of terrestrial vegetation in the great beds of 

 Laurentian iron-ore which show subaerial decay, thus implying the 

 " reducing and solvent action of substances produced in the decay 

 of plants." Dr. Dawson long ago (1875) believed that he had found, 

 in the compact graphitic limestones of Clarendon, traces of fibrous 

 structure due to segregation which may be the remains of plants, 

 " and in some specimens vermicular lines " which he believed to be 

 " Eozoon penetrated by matter once bituminous, but now in the 

 state of graphite." At the utmost we can only speculate upon the 

 presence or condition of vegetation during the Archsean, or Pre- 

 Cambrian, Laurentian, or Eozoic time. 



Dana employs the term Archaean in time, to express in full mean- 

 ing that era in the physical development of the Earth which was 

 "incompatible with the existence of life," when life was not, so far as 

 we know. Little, however, is known of that vast group of rocks 

 we call Pre-Cambrian, adopting this term as used in this country, 

 on the Continent, and in America, for rocks affording us no history 

 or recognizable records. 



Dana again assumes and endeavours to show that four eras pre- 

 ceded the Laurentian period : — 



A first or molten era subsequent to that of the presumed original 

 nebulous state. 



A second era, one of solidification and consolidation through 

 cooling, when the Earth became solid at the centre ; later on, at- 

 mospheric vapours became condensed and probably universal ; water 

 covered all. The cooling and contracting of the sphere resulted in 

 oceanic depressions in special areas, and our continents were sha- 

 dowed forth and contoured, but as yet no life can be chronicled. 



The third era may have given us surface reliefs : stratified deposits 

 were formed. 



The fourth era probably saw the beginning of life, which occurred 

 when the oceanic waters may have stood at 200° E. With this 

 fourth era we may associate the Eozoonal serpentines. 



In the British Islands we have yet to find that type of Laurentian 

 rock which yields either of the great limestones of Canada, — 

 the so-called Fundamental Gneiss of Scotland, Malvern, and Ire- 

 land having no affinities with the Eozoonal and graphitic group 

 of the North- American continent, and being doubtless of vastly 

 younger date. 



To summarize the results of the labours and views of those who 

 vol. xxxvn. f 



