MAGNETIC OXIDE OF IRON. 



21. 



89 



a, Mass from which the veins of ore proceed ; 6, Rock. 



beneath the adjacent rock, if appearances are not deceptive. If so, it is a step towards proving 

 the diversity of materials in the earth, and accounting for the greater gravity of tiie earth as a 

 whole, than that of its crust. 



So httle can be determined by observation, that rehance cannot be placed on speculations 

 of this kind. The naked fact is, that after tracing the ore continuously for five or six hundred 

 feet, it disappears under the rock of the countr3^ How far it extends, and what is the nature 

 of the termination, cannot be known until the upper rock is removed. Neither do we know 

 much in relation to its depth, from actual inspection ; for none of the masses in this region 

 have been penetrated more than twenty or thirty feet. But in this distance, two important 

 facts are revealed : 1st, that the ore becomes purer and richer ; and 2d, that portions of rock, 



22. 



Mass of fine-grained ore at Adirondack. 



which projected into the mass, disappear. I have, in the annexed diagram, represented this 

 fact, as it appears in one of the excavations at Adirondack. The mass often presents the 

 appearance of stratification, being divided by planes into layers from four to ten inches thick, 

 parallel with which is the layer of rock b. This layer, however, was thicker at the surface, 



Geol. 2d Dist. 12 



