ORES OF FIVE MINOR METALS 115 
cementing broken pieces of the silicates and country rock, 
or replacing those materials and especially the biotite. 
According to C. W. Knight, the one fact that may be stated 
"with certainty is that the sulphides were introduced after 
the norite-micropegmatite had solidified. This is proved 
beyond doubt ** (C. W. Knight, Rep. Ontario Nickel Comm., 
1017, p. 113). The ore bodies form lenticles, pipes, or 
veins; they are arranged in two groups, one near the margin 
of the gabbro, and the other in “off-set ”’ bodies away from 
It. Most interest was at first paid to the marginal ore bodies, 
and they were explained as due to the heavier magma hav- 
Ing sunk to the base forming the gabbro, while the lighter 
floated up to form the micro-pegmatite, and to the metallic 
sulphides having collected at the base of the molten gabbro. 
The off-set bodies were regarded as dykes from the lower 
Part of the gabbro. This origin for the ore was suggested 
by D. C. Davies in 1883 and by F. D. Adams (G.S. Canada, 
V1, 1893, p. 13), and for the basic rock as well by T. L. Walker 
(0.57.G.S, liii, 1897, pp. 52, 56). This theory was authorita- 
tively advocated by Barlow and Coleman. The igneous origin 
of the ores has been adopted in recent years in a modified 
form by Tolman and Rogers (Stanford Univ. Publ., 1916), who 
regard the ores as having been formed later than the gabbro 
by magmatic solutions, and by Spurr who describes the ores 
as ““veindikes "’ (Ore Magmas, 1923, p. 567); E. Howe 
(Econ. Geol., ix, 1914, p. 514) and A. M. Bateman (ibid., 
XIX, 1024, pp. 504-20) accepted part of the sulphides as intro- 
duced in solution, but consider that part was injected in a 
molten state, 
The igneous theory was early rejected by Posepny (1891), 
Beck (1901), and by C. W. Dickson in 1903 (Tr. Amer. 
LM.E., xxxiv, 1903, pp. 3-67), who published evidence 
that the sulphides were the last constituents to solidify and 
Not the first. This view was expressed by the author 
(Presid. Address Geol. Sect. British Assoc., 1907, p. 499, 
and 1 1909 at the discussion on the question at the British 
Association in Winnipeg ; also Geol. Mag., 1908, p. 40, and in 
Physical Chem. Rock Formation,” Tr. Faraday Soc., xx, 
1924, pp. 454-6). The igneous theory has been emphatically 
rejected as opposed to both the field and microscopic evi- 
dence by C. W. Knight (1917, Rep. Ontario Nickel Commission,