28 THE CANADIAN NATURALIST. [Vol. ix. 



and RawdoD, Grenville and Hastings in Canada — are parts of 

 one great series, and at present I see no evidence for excluding 

 from this series the associated Norian rocks. Whether the series 

 as a whole will eventually retain the name Upper Laurentian or 

 whether it will be found to be more convenient to desio^nate it 

 Huronian System does not much signify. 



We can, however, confidently state that this series occupies 

 an unconformable position between a massive gneiss formation 

 below and unaltered Potsdam or Lower Silurian rocks above, 

 and this may likewise be stated respecting the ^stratigraphi- 

 cal position of the typical "Huronian series" of the Georgian 

 Bay, which together with its close proximity to the western-most 

 known exposures of the crystalline Laurentian limestone series 

 which we now know, extends from Parry Sound to Lake Nip- 

 pising, and includes some Labradorite gneiss, renders it very 

 probable that a connection will eventually be traced out between 

 even these supposed greatly different formations, similar to that 

 now, as already stated, proved to exist between the Hastings and 

 Grenville series. 



Prof. Hall in his note already referred to, states that the La- 

 bradorite formation is "associated" with bands of crystalline 

 limestone, and further on that the limestones do not belong to 

 either the upper or lower Laurentian. He does not however say 

 what the upper Laurentian he alludes to is, though in another 

 paragraph we find it stated that the " lower Laurentians are 

 succeeded by massive beds of Labradorite," which we may infer 

 are considered upper Laurentian, in which case there would 

 seem to be, in New York State two sets of Labradorite rocks, 

 one associated with the limestones which are "altogether newer 

 than Laurentian," and another massive and representing upper 

 Laurentian. There is, however, so far as I am aware, no evi- 

 dence of this being the case in Canada. If it is admitted — which, 

 in view of the usual associations of Labrador feldspars, is the 

 most probable supposition — that these anorthosite rocks represent 

 the volcanic and intrusive rocks of the Laurentian period then also 

 their often massive and irre(2:ular and sometimes bedded character 

 and their occasionally interrupting and cutting off some of the 

 limestone bauds as described by Sir W. Logan, is readily under- 

 stood by any one who has studied the stratigraphical relations of 

 contemporaneous volcanic and sedimentary strata, of paleozoic, 

 mesozoic, tertiary and recent periods. Chemical and microscop- 



