362 GEOLOGY OF THE DEXVEE BASIN. 



composite seam that there is in the Lafayette region. The individual seams, 

 3 and 4, are still generally identifiable by position, but vary in thickness from 

 1 foot to 3 feet and 3 feet to 6 feet, respectively, and this with rapidity 

 and comparative frequency. The parting separating the two seams varies 

 from 1 inch to its maximum width, "Jo feet. A study of the sections of 

 tlic Louisville district. PI. XVII, clearly illustrates these features, for, from 

 the nearest approach to the union of the seams — in the Acme, Caledonia, 

 and Welch mines — and from a comparatively well-developed thickness, 

 every gradation is observed to the opposite extremes, which occur in the 

 vicinity of the Ajax and Marshall Consolidated shafts, where thickness of 

 seams is reduced to a minimum and the mass of separating rock has 

 increased to the maximum. It is a condition worthy of note in the mines 

 of the Louisville and Lafayette districts that where the individual seams 

 are no longer closely united in a mammoth seam they are inclined to 

 become divided In - partings, and that they are the more divided as separa- 

 tion of the primary seams increases. 



The manner in which the component seams, o and 4, and their asso- 

 ciated sandy and clayey beds sometimes vary is well illustrated in the 

 Marshall Consolidated mine. (Figs. F, (4, H, PI. XX.) In passing from 

 the shaft westward along the main entry, the lower seam is found to have 

 widened from "J feet 6 inches to ."> feet 6 inches in a distance of 1,200 feet; 

 the upper seam, after a decrease from .'> feet to 1 foot, 400 feet west of the 

 shaft, has again widened to 2 feet 6 inches at a point 1,200 feet west; Avhile 

 the intervening series of sandstone ami slate, which is 20 feet thick at the 

 shaft and without coal, has at a distance of loo feet west decreased to a 

 total width of about 3 feet 6 inches, with one or two impure coal streaks, 

 and at 1,200 feet is only 1 inch thick. 



Regarding the identity of the component seams in the Marshall Con- 

 solidated and Ajax mines, no question exists as to that of the lower; the 

 correlation of the upper, however, is in places attended with some uncer- 

 tainty on account of occasional parting's that exist in the individual seams 

 which can not he traced through from mine to mine, and so lead to a 

 confusion between the beds. The Ajax presents the most serious difficulty 

 in this respect. 



