334 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



Logan evidently held that the greenish slates (No. 3) were conform- 

 able to and continuous with the underlying gneiss, one rock passing 

 into the other ; while the conglomerates observed were not at the base 

 of the slates, but quite high in the series. (Geol. of Canada, 1863, 

 pp. 52-55, 64.) Dr. Hunt's language in his " Azoic Rocks " (p. 68) 

 implies that Logan found a different relation between the gneiss and 

 slate, — namely, unconformability with the conglomerate at the base. 



Ml'. Alexander Murray in the same report (1846-47) states that the 

 rocks in the basin of the Kamanistiquia River are granite, syenite, 

 gneiss, micaceous and chloritic schist, overlain by blackish argillaceous 

 slates with associated trap. 



Of the first series he says : — 



" Where they make their appearance at the lower end of the portage, the 

 character of the rock is a red or m some instances a whitish massive syenite, 

 which passes gradually into a gray gneissoid syenite, dipping at a high angle 

 N. N. W. Resting conformably on the gneiss, there occurs a series of dark 

 greenish blue or greenish black altered slates, the one rock passing almost im- 

 perceptibly into the other Towards the bottom near the junction with 



the syeuitic portion, the slates are of a dark bluish and occasionally of a brown- 

 ish color. They appear to be highly altered." 



Of the black argillaceous slates Mr. Murray says : — 



" The base of this formation .... was observed on the Kamanitiquia near 

 the Grand Falls. Its immediate junction with the rock on which it reposes 

 was concealed from view, but appears to be indicated by the position of a small 

 lake or pond, occurring just below the second portage, and the marshy ravines 

 which run from it in the direction of the strike on each side. The slates vis- 

 ibly reach to Avithin a short distance of the pond, probably brought into place 

 against the syenite by a dislocation." (/. c, pp. 51-53.) 



The syenite and gneiss afterwards were assigned to the Laurentian, 

 and the greenish blue or greenish black slates to the Huronian. Hence 

 we see that at the only contact known for many years of the Laurentian 

 and Huronian both series were conformable, 2mssi?ig almost impercejitibly 

 into one another. Also, that near the junction the slates were highly 

 altered. (Geol. of Canada, 1863, p. 64.) These fticts are not men- 

 tioned by Dr. Hunt in his account of this report. (Azoic Rocks, pp. 

 68, 69.) It is, however, to be kept in mind, that at this time, as also 

 when the Huronian was named and for some years later, Nos. 4 and 5, 

 or the black slates, sandstones, traps, conglomerates, etc., constituting 

 the copper-bearing series (Keweenawan, but really Potsdam) were held 

 to be the exact equivalents of the schists and slates (Huronian) north of 



