The Magnetite Belt at Cranberry, N. C — Kinihall. 311 
British Columbia* and have referred to still others in cul- 
minating regions of the Cascade Mts. of Washington. 
These several examples falling under my own observation, 
together with the very notable occurrences at Cranberr}^, all 
illustrate, though on widely different scales of economic im- 
portance, local differentiation of iron ores due to hydro-chemi- 
cal or so-called metasomatic permutations. Beyond the ulti- 
mate effect produced, in neither example is there much in 
common with orujinal differentiation of magnetite and basic 
silicates from eruptive magmas as claimed by Brogger and by 
Vogt to have been the mode of genesis of certain magnetic iron 
ores in Norway and Sweden. Assuming for the moment the 
correctness of the conclusions of these excellent observers, it 
will be perceived that apart from conditions of magnitude 
and importance the occurrences above noticed closel}^ simu- 
late the isolation or concentration of titaniferous magnetite 
graduating, as shown by these authors, from this extreme of 
basicity to less basic and finally acid differentiations from 
eruptive magmas. Yet on general grounds it seems open to 
suspect that even in the examples given by Vogt dift'erentia- 
tion of iron ores at least may have been accentuated if not 
produced by slow progressive molecular or metasomatic alter- 
ation and replacement. Among identical secondary products 
alike from eruptive rocks, and from progressive alteration or 
molecular -deformation of clastic rocks are magnetic and 
specular oxides of iron from basic material indifferently, 
whether eruptive or metamorphic. The instability of basic 
rocks of either classification compels extreme caution in de- 
ciding between primary rocks of this description aud deriva- 
tive products. I have taken previous occasion to comment 
more particularly on the same important point. f 
The genesis of magnetite at Cranberry both concentrated 
and more or less blended proceeded hydro-chemically, as may 
be conceived, from an originall}^ basic aggregate — in part 
during the process of induration and crystallization, and 
likewise subsequently and even secularly, aided perhaps by 
molecular affinity and especially by mutual attraction and 
flow of magnetic molecules. Evolution of the magnetic oxide 
of iron from protoxide in uni-silicates is proof that here, as in 
*Vol. XX, 1897, p. 13. ~~ 
tAm. Jour. Sc. [3] xxviii, 429. 
