246 GEOLOGY OF THE SECOND DISTRICT. 



in the quality of the ore which they furnish : different parts of the same vein appear to have 

 different quahties, which often arise from causes not well understood ; for example, where a 

 trap dyke cuts through a mass of ore, it always changes the mode of its working, and, I 

 believe, invariably increases the difficulty of its reduction ; and when reduced, it makes a 

 a harder iron. The great veins of Adirondack, however, present a high degree of uniformity 

 in the texture of their ores, in their mode of working, and in the quality of the resulting metal, 

 and this uniformity is only equalled by a few of the minor beds in the counties of Essex 

 and Clinton. This I conceive to be a very important fact ; for it is perfectly plain that great 

 advantages will always arise from uniformity in these respects, especially the latter. 



Again, the ores of all the beds of much consequence have a jointed structure, and break 

 into tabular masses, and in this respect resemble the stratified rocks. This structure is not, 

 however, due to stratification, but probably to crystallization ; and it is also probable that 

 this kind of structure is more distinct near the surface, and that as the beds are worked, 

 less of it will appear. This will have some effect in the facility of raising the ore, which will 

 become more compact the deeper the vein is worked, and freer from the seams or divisions 

 necessary to allow the masses of ore to be laid hold of, in order to effect their separation from 

 each other in certain directions. 



My examination of the relative position of these veins or beds has never enabled me to deter- 

 mine whether the mass, as a whole, had a dip and line of bearing, or not. It will be seen by an 

 inspection of one of the places, that minor veins occasionally project from the main mass, and 

 pursue a given direction ; but where our observations have been directed to a vein as a whole, 

 it has been very often followed by uncertainty whether it pursued, like an ordinary vein, a 

 course which could be denominated its strike or line of bearing. A difficulty which of course 

 contributes mainly to this result, is the uncertainty of distinct walls ; and where a mass of 

 rock appears bounding the ore on one side, whether it was truly a wall, or a mass of rock in 

 the midst of the bed or vein ; inasmuch, too, as such masses are not unfrequent, and, in the 

 course of mining, run out, and disappear entirely from the vein. From this fact, it will be 

 perceived how it happens that I have expressed myself vaguely in regard to the point whether 

 these masses are truly veins ; and as we have no assistance in determining the question from 

 the presence of walls, except in some veins subordinate to a large mass, so we have none in 

 the direction in which the outcrop of the ore appears on the surface ; for though they are often 

 situated in imperfect ranges as it regards each other, yet it is not clear that masses so situated 

 arc really beds or veins prolonged in such a direction. 



In all the uncertainty which lies over this subject, I am more disposed to believe that the 

 whole valley of the Adirondack river is underlaid by the magnetic oxide. It is true that this 

 belief borders on the extravagant, particularly when it is first suggested ; but after all, where 

 is the extravagance in supposing that a mountain may be composed of iron ore, or a valley 

 underlaid with it ? For aught that appears to the contrary, the interior of the earth may as 

 well be composed of ore, as of rock or stony matter. In confirmation of the opinion 

 expressed above, I shall have occasion to state many facts in the following pages. 



