THE LAUEENTIAN EOCKS. 27 



Lower and Upper Laurentian rocks spread over more than 

 200,000 square miles in Canada, only about 1500 square miles 

 have yet been fully and connectedly examined in any one 

 district, and it is still impossible to say whether the numerous 

 exposures of Laurentian limestone met with in other parts of 

 the province are equivalent to any of the three zones, or 

 whether they overlie or underlie them all." 



(B.) De. Steeet Hunt on the Peobable Existence of 



LiPE IN THE LaTJEENTIAN PeEIOD. 



Dr. Hunt's views on this subject were expressed in the 

 American Journal of Science, [2], vol. xxxi., p. 395. From this 

 article, written in 1861, after the announcement of the exist- 

 ence of laminated forms supposed to be organic in the Lauren- 

 tian, by Sir W. E. Logan, but before their structure and 

 affinities had been ascertained, I quote the following sen- 

 tences : — 



" We see in the Laurentian series beds and veins of metallic 

 sulphurets, precisely as in more recent formations ; and the 

 extensive beds of iron ore, hundreds of feet thick, which 

 abound in that ancient system, correspond not only to great 

 volumes of strata deprived of that metal, but, as we may 

 suppose, to organic matters which, but for the then great 

 diffusion of iron-oxyd in conditions favourable for their oxi- 

 dation, might have formed deposits of mineral carbon far 

 more extensive than those beds of plumbago which we actually 

 meet in the Laurentian strata. All these conditions lead us 

 then to conclude the existence of an abundant vegetation 

 during the Laurentian period. 



(C.) The Geaphite of the Laueentian. 



The following is from a paper by the author, in the Journal 

 of the Geological Society, for February, 1870: — 



" The graphite of the Laurentian of Canada occurs both in 

 beds and in veins, and in such a manner as to show that its 

 origin and deposition are contemporaneous with those of th:§ 



