THE LAURENTIAN ROCKS. 33 



of cellular plants, as, for example, mosses and lichens ; and if 

 so, there would be comparatively little hope of the distinct 

 preservation of their forms or tissues, or of our being able 

 distinguish the remains of land-plants from those of Algae. 

 "We may sum up these facts and considerations in the 



)llowing statements : — First, that somewhat obscure traces of 

 organic structure can be detected in the Laurentian graphite ; 



jcondly, that the general arrangement and microscopic struc- 

 re of the substance corresponds with that of the carbon- 



3eous and bituminous matters in marine formations of more 



lodern date; thirdly, that if the Laurentian graphite has 

 )een derived from vegetable matter, it has only undergone a 



letamorphosis 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 

 )rganic limestone, beds of iron ore, and metallic sulphides, 



reatly strengthens the probability of its vegetable origin; 



^thly, that when we consider the immense thickness and 



[tent of the Eozoonal and graphitic limestones and iron ore 

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

 bhe limestone and graphite, we must be prepared to believe 

 that the life of that early period, though it may have ex- 

 isted under low forms, was most copiously developed, and 

 it it equalled, perhaps surpassed, in its results, in the way 

 )f geological accumulation, that of any subsequent period." 



(D.) Western and other Laurentian Eocks, etc. 



In the map of the Laurentian nucleus of America (fig. 4,) 

 tt have not inserted the Laurentian rocks believed to exist in 

 [the Eocky Mountains and other western ranges. Their dis- 

 rtribution is at present uncertain, as well as the date of their 

 [elevation. They may indicate an old line of Laurentian 



fracture or wrinkling, parallel to the west coast, and defining 

 pts direction. In the map there should be a patch of Lauren- 



bian in the north of Newfoundland, and it should be wider at 

 Ithe west end of lake Superior. 



Full details as to the Laurentian rocks of Canada and sec- 



