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fication of the rock, this being the direction in which the strata 

 would most readily give way. If the rule be a general one, that 

 these veins range and dip parallel to the strata, we are led to 

 some important general hints for seeking and opening mines in 

 this region. One is, that the veins of ore may be expected to 

 follow the same layer or bed of rock for a considerable distance ; 

 and that the nature, therefore, of the adjoining rock, will often 

 prove a clue for finding a previously known vein in the direction 

 towards which it is prolonged. Another suggestion is, that when 

 levels are cut, or shafts sunk to reach a vein, the indications of 

 which are witnessed upon the surface, the excavations should be 

 made on that side of the presumed outcrop of the vein which is 

 towards the underlie, or dip of the gneiss, because the vein, keep- 

 ing parallel wi'th the rock, will descend in that direction. 



Respecting the geological date of these veins of magnetic iron 

 ore, it seems difficult, from the imperfect nature of the data 

 afforded by the region, to arrive at positive conclusions. The 

 views which we here venture to suggest in the light of the hypo- 

 thesis on the subject, are offered as merely conjectural. They 

 are deemed at the same time worthy of a place in our account 

 of the geology of the Highlands, as assisting to throw light upon 

 other questions hereafter to arise, and as opening a train of in- 

 quiry interesting to future investigators — some of whom, let us 

 hope, may hereafter find an inviting field for research in the 

 structure and former physical history of this mountain belt. 



In examining the question of the date of the veins of magnetic 

 iron ore, our attention is at once called to the interesting general 

 fact, that these veins lie exclusively in the primary rocks. I think 

 we must conclude, that most, if not all of these veins of ore, were 

 etruded from their deep source beneath the surface, during the 

 epochs which preceded the deposition of the first widely dispersed 

 secondary strata. 



CHEMICAL COMPOSITION OF THE MAGNETIC IRON ORES OF THE 

 HIGHLANDS. 



Suggestions concerning the treatment of these ores, can be of 

 service to the manufacturer only in proportion as they are the 

 results of numerous and precise chemical investigations into their 

 composition. 



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