760 A. P. COLEMAN 
many geologists do not receive these reports, it is proposed to give 
here a condensed account of the nickel-bearing eruptive and its 
general relationships to the rocks of the region. 
It was quickly discovered by prospectors for nickel that all the ore 
deposits are associated with bands of a particular basic rock, at first 
called diorite, but later found to be norite. The district was mapped 
in 1890 by Dr. Bell, with Dr. Barlow and other assistants, and their 
work brought out clearly some of the features just mentioned. Two 
main bands of the nickel-bearing eruptive were indicated, a northern 
and a southern, or main, range, running with some interruptions 
parallel to one another in a northeasterly and southwesterly direction.* 
In 1893 a great advance was made in our knowledge of these rela- 
tionships by Professor T. L. Walker, who showed that the norite 
associated with ore passes into micropegmatite, and also that the 
transition from norite to granite takes place from south to north in 
the main range, and in the reverse direction in the northern range.’ 
My own field-work, begun in 1902, proved that the two ranges 
are connected at the ends, forming an irregular oval, and as the 
results of three summers in the field, the upper and lower boundaries 
of the sheet were mapped, the only important gap occurring for about 
two miles at the east end, where the solid rocks are concealed by 
drift. This work has proved also that the sheet is basin-shaped, since 
the lower or basic edge everywhere dips inward; and that the ore 
deposits are all at the lowest points of the basic edge, showing that 
segregation took place by the aid of gravity.’ 
Dr. Barlow’s report, which appeared in 1904, confirms these 
results as far as the southern range is concerned and gives an exhaus- 
tive account of the petrography of the region and the development 
of the nickel industry. It should be consulted by anyone interested 
in nickel.4 
SHAPE AND SIZE OF THE SHEET 
The norite micropegmatite sheet forms an irregular synclinal 
basin, somewhat boat-shaped or spoon-shaped, to borrow Dr. Daly’s 
I Geological Survey of Canada, 1890, Part F. 
2 Quarterly Journal of the Geological Society of London, Vol. LIII, pp. 40-46. 
3 Bureau of Mines, 1903, pp. 276-78, and 1904, pp. 193, 194. 
4 Geological Survey of Canada, 1904, Part H. 
