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that some differences of character also present themselves. This will 
appear more evident, v^^hen it is known that the ore of the same vein 
is far from being uniform in its characters. These differences are 
sometimes favorable, and sometimes unfavorable. The passage of a 
dyke through a vein changes the character of the ore to a certain ex- 
tent ; and so far as I have conversed with miners, or proprietors of 
mines, no satisfactory explanation has yet been given, of this fact. 
Veins are rarely, if ever, composed of ore in a uniform state of aggre- 
gation ; in some portions it is compact, in others granular, varying from 
coarse to fine. 
There is, however, some degree of uniformity, sufficiently so, to give 
a general character to the vein ; thus one of the veins at Arnold hill, is 
called the old blue ore, and we call one of the veins at Mclntyre, the 
coarse black ore, and another, the fine ore, which characters they pre- 
serve as a whole. 
In remarking the differences which the veins of ore present, it is pro- 
per to notice one, which evidently depends on chemical constitution. 
Generally, it has been already remarked, the ore gives a black streak 
when scratched, or a red powder when pulverized. This is not the case 
in the Arnold ore, though in the analysis which have been given to the 
public, scarcely any difference appears in its chemical constitution, from 
those which give the black streak. It would, however, appear to be 
composed of a greater proportion of the peroxide of iron, if the colour 
of the powder be a test of the state of oxidation. In its external cha- 
racter, the Arnold vein does not differ essentially, from the ordinary 
magnetic oxide. Its general crystalline form is that of the magnetic 
oxide, and as it presents no indication of the rhombic form of the spe- 
cular ore, it is evidently the species already referred to. If any change 
has taken place in the ore, it is that which results from the absorption 
of oxygen, by the portion in a state of a protoxide, and one, which has 
taken place at a period subsequent to its deposition in the vein. 
SECTION VII. 
Qualities of the ore helo7iging to different veins. 
Extended experience has estabhshed the fact, that the ore of different 
veins, though of the same mineralogical species, produces iron of differ- 
ent qualities, even when the mode of manufacture, is as near as possible 
after one form. As a general rule, the granular varieties, produce the 
softest irori, and the tough or hard, a hard and brittle iron. Besides, 
