OF PRE-CAMBRIAN ROCKS 203 
other minerals. ‘The committee therefore considers this conglomerate 
to be of interformational origin, and to have no special structural 
significance. 
The committee then proceeded by train to Ormsby, where they 
examined a remarkable development of the limestone series consist- 
ing of beds of limestone interstratified with thin bands of amphibolite, 
displaying a series of very intricate folds. They also examined the 
Thanet gabbro, a large intrusive mass of approximately circular 
outline which here breaks through the limestone series, sending dykes 
into it and including masses of the latter. They also visited the 
Coehill iron mines, situated about five miles to the west of the village 
of Ormsby, where a very considerable body of somewhat pyritiferous 
magnetite is developed in the limestones, here interstratified with 
amphibolite about the contact of an intrusive mass of syenite. 
Between Ormsby and Ormsby Junction the committee saw a great 
development of the typical rusty gneiss which is so commonly associ- 
ated with the white crystalline limestones wherever these occur in 
the area embraced by the work of the committee. The development 
of these gneisses at this locality is one of the thickest which have 
hitherto been discovered in this series. Some bands of it resemble 
in appearance certain varieties of the Magnetite-Grunerite Schist 
of the Lake Superior iron ranges. 
From Ormsby Junction the party went north by railway, passing 
over a further extension of the limestone series to Bancroft on the 
York branch of the Madawaska River, and examined the nepheline 
syenites, which have a very extended development in this district, 
and which in one locality about two miles and a half on the east of 
Bancroft are traversed by veins containing large masses of sodalite 
which are now being worked for decorative purposes. 
They then went east to Bronson’s Landing and proceeded by 
canoes down the York branch of the Madawaska to Craigmont, and 
spent three days in examining the very extensive and highly interest- 
ing occurrences of corundum which are here being mined on an exten- 
sive scale. This corundum occurs in syenites, most of which are 
rich in nepheline. 
The party then returned to Bancroft and went by the Irondale, 
Bancroft & Ottawa Railway to Gooderham, stopping on the way to 
