ANNIVERSARY ADDRESS OF THE PRESIDENT. IxiX 



Upon careful study of the Appalachian zone, as the Professor terms 

 that region, one having a length of about 1300 miles and a mean 

 breadth of 150 miles (an area therefore of about 195,000 square miles), 

 he and Prof. W. B. Rogers found that it was marked by five great 

 belts. These, when crossed from S.E. to N.W,, exhibited the greater 

 flexures in the first belt, or that on the S.E. of the Blue Ridge or 

 Green Mountain Chain and within this chain, old semi-crystalline 

 schists and the oldest palaeozoic rocks were doubled into enormous, 

 closely-compressed, alternate folds, dipping almost exclusively to the 

 S.E. at angles varying from 45° to 70°. In the third belt, the oblique 

 flexures of the older palaeozoic rocks are less compressed, the north- 

 western side of each anticlinal curve approaching near to verticality. 

 In the fourth belt, that of the central Appalachians of Pennsylvania, 

 Virginia and Tennessee, the convex and concave flexures progressively 

 expand, the steepness of the N.W. side of each anticlinal gradually 

 diminishing. In the fifth belt, that of the bituminous coal region of 

 the Alleghany and Cumberland mountains, the curves dilate and sub- 

 side into broad symmetrical undulations with very gentle dips. We 

 thus have five belts ; the greatest flexures and folds in that on the S.E., 

 the least in that on the N.W., the prevailing dip towards the S.E. 

 Prof. Rogers then showed that the folds and undulations of the strata 

 lie in groups, the several axes being very nearl}^ parallel and similar in 

 their style of flexure, many of the larger anticlinals having a length 

 of 80 or 100 miles. With regard to the distances of the contiguous 

 great folds, they are stated to be, in the south-eastern belt, less than 

 one mile ; in the central belt between one and two miles ; and in the 

 north-western belt the flexures have an amplitude of from five to ten 

 miles. With regard to dislocations of the beds, two systems are 

 noticed — one of short fractures, nearly perpendicular to the strike of 

 the anticlinals ; the other ranging with them, and often of consider- 

 able amount. The longitudinal dislocations, some in Virginia having 

 a length exceeding 100 miles, are considered as broken flexures, the 

 fracture almost invariably occurring on the north-western or inverted 

 sides of the anticlinals, and having a moderately steep south-eastern 

 dip. Some of these great fractures constitute faults of not less than 

 8000 feet. 



Upon looking at all the facts adduced by the Professors Rogers, 

 who have thus so well worked out the flexures and fractures of the 

 rocks composing this part of the United States, we cannot but be 

 struck with the evidence of an exertion of force along a line no less 

 than 1 300 miles in length, folding the component beds of rocks in such 

 a manner as to show that the eff'ects of that force gradually diminished 

 towards a parallel line some 150 or 200 miles distant on the N.W. 

 from the first line. We have thus some 200,000 square miles of 

 rocks, the thickness of which we do not know, though from faults 

 being ascertained of as much as 8000 feet, we may at least give them 

 a mile and a half in depth, ridged and furrowed in great parallel bands, 

 with minor flexures dependent on the same great exertion of force. 

 The efl*ects produced, for the careful examination and full description 

 of which we are so much indebted to the Professors Rogers, are also 



