nick's creek ikox oke kegiox. 



45 



the lowest water level of the region, has been calculated as for the aforementioned 

 beds, and is : On the north side of the Brushy Mountain Saddle 2,840,000 tons ; on 

 the south side of the Pond Mountain Saddle 3,990,000 tons ; on the north side of the 

 same 3,050,000 tons ; on the little saddle next to the north 930,000 tons ; making in 

 all, 10,810,000 tons for every average foot of bed. 



The bed may be taken, from the exposures of it that have been described, to be 

 pretty uniformly of good thickness and of fine quality throughout the region. It is 

 impossible to state, however, without more thorough trial ]3its, what that thiclmess is 

 in feet on the average, and what consequently should be the multiplier of the num- 

 ber of tons just given, to get the full amount of ore in the bed above water level ; but 

 it would seem to be perhaps ten feet, to judge by the best exposures alone. 



ALL FOUR ORE BEDS. — Modc of Occurrence. 



The mode of occurrence of these ores has already been discussed in a paper read 

 at the Burlington meeting of the American Association for the Advancement of 

 Science, 1867, vol. xvi., p. 114. Three parallel cross-sections show that the thirty or 

 more ore banks and natural exposures occur at corresponding distances on the 

 opposite sides of the Pond Mountain Saddle and of the basin south of it, as if they 

 were the outcrops of four beds of ore conformable to the other rocks. At three or 

 four of the ore banks the solid beds are to be seen, but at the other exposures the ore 

 is in solid lumps of irregular shape and of every weight up to three hundred tons or 

 more, scattered irregularly through brown gravelly loam. The ore (all brown hema- 

 tite) is sometimes very pure, but often has in it rounded or, angular grains or pebbles 

 of white quartz, and sometimes is merely a cement that binds together angular pieces 

 of light brown sandstone. 



The deposits of loose lumps in this region seem to resemble in every respect those 

 that are so common throughout the Great Valley of Virginia, and its prolongation 

 northeastward as well as southwestward. They seem beyond a doubt to be the 

 broken pieces from the outcrops of solid beds of ore and of the same character as 

 accumulations of outcrop blocks of any bed of rock or the black dirt of a coal out- 

 crop, or alluvial deposits of gold or tin ore, due regard had to the effect of the special 

 hardness, bulk and weight of the iron ore. They do not by any means seem to come, 

 as has been maintained, from the mere percolation of water through slates impreg- 

 nated with iron, which is dissolved and carried into the loam and afterwards segre- 

 gated in a remarkably perfect way. 



Of course, the strength of the argument furnished by the ores of the region, de- 

 pends partly on the exactness of the survey ; but although this was only rough, the 



A. p. S. — ^YOL. XV. L. 



