68 GEOLOGICAL SURVEY OF ALABAMA. 



clearly outlining its structure, yet owing to certain irregu- 

 larities of level and of faulting, this lias not in all cases been 

 clearly accomplished. 



The greatest difficulty in identifying seams was found 

 along the southeastern base of Straight Mountain, where a 

 fault of varying and uncertain depth exists. This fault 

 partly exposes, but also dissevers the mountain from, the 

 northwestern edge of the productive coal measures. Several 

 important coal seams are found in close connection with this 

 line of fault which as yet can be only doubtfully referred to 

 their proper position in the field. 



Among these doubtful seams is the Waide seam already 

 described under the head of "Explorations" (page 23). It 

 was doubtfully referred to No. 8 of the General Section under 

 the head of Details. That reference was made solely on the 

 similarity of the surroundings, the cap-rock and intervening 

 slates, the coal seam being under deep water, and unseen. 

 Could the coal seam have been examined at this, or other 

 places in the river where it was presumed to come near the 

 surface, and to be cut by the water in deep places, fuller 

 evidence of identity would probably have been obtained. 

 Usually the surroundings of a coal seam, the overlying 

 slates and cap-rock, afford better evidence of identity than 

 the size and structure of the coal seam itself. The latter 

 may vary from place to place in quality, thickness and part- 

 ings, all produced from local inflows of sediment during the 

 period of its formation; the former resulting from a general 

 inflow of sedimentary covering, more widespread, uniform 

 and persistent, necessarily give characteristics of greater 

 uniformity. From these surroundings alone, and from the 

 further fact that no other seam of coal possessed similar sur- 

 roundings in that part of the field where its outcrop must 

 necessarily come to the surface, this one was without much 

 doubt referred to the Waide seam No. 8. This would, if 

 accepted as sufficient evidence, fix its southeastern outcrop 

 in nearly a southeast course from the Waide Gap where it 



