272 NOVA SCOTIAN GEOLOGY—HONEYMAN. 
examine the gneissic boulders in my “ Boulder Collection.”— 
Superficial Geology.—Trans. 1876-7. 
In one boulder from the drift of the west side of MeNab’s 
Island, Halifax Harbour, I also found grains of magnetite. The 
specimen has a decided eneissic structure with the lines much 
contorted, whereas the lines of the specimens already noticed 
are sub-parallel. The boulder consists of red orthoclase and 
green hornblende, with a little quartz and mica. Grains of mag- 
netite are scattered throughout. This boulder is, beyond doubt, 
from the Cobequid gneisses, having travelled at least 65 miles 
to reach MeNab’s Island. The proof of this is to be found in 
the paper cited. 
The occurrence of magnetite in these gneisses enables me to 
indicate precisely the southern limit of the Archzean formation. 
The associated diorites extend southward to the bridge above 
Acadia mines. <A northern limit point is evidently the north side 
of Smith's cutting, Wentworth, IC. R. Here there is a great 
development of diorites with porphyrites, instead of gneisses 
of the south side. This gives the whole Archean, according 
‘to the I. C. R. plans and section books, before me, a width of 
five miles. 
OTHER PRE-CARBONIFEROUS FORMATIONS. 
These occur on both sides of the Archzean, north and south, 
in the Intercolonial Railway section. 
Although the position of the first on either side and apparent 
sequence might lead to the supposition that the formations cor- 
respond, lithology makes a decided distinction. As neither is 
fossiliferous, palzeontology lends no aid, pro or con, in the cor- 
relation of the two. 
The lithology and sequence of the formation on the north, 
Wentworth, side led me, when I first examined the rocks of the 
I. C. R. section, to recognise a correspondence with a peculiar 
formation in the Arisaig Mountains, which had caused consider- 
able perplexity on account of its position and peculiarity. It 
occupies an intermediate position between the Archean, which 
I had designated the “ Lower Arisaig Series,” and the fossilifer- 
ous middle and upper silurian, which I had named the “ Upper 
