1894.] ^^' [Lyman. 



strike and elevation of each exposure, and proceeding from point to point 

 between the nearest ones, so that no essential error could occur from 

 changes of dip or strike in so small a space, and checking occasionally 

 the computation between two distant points over one route by like compu- 

 tations over another route, with the aid sometimes of a comparison of 

 specimens to identify the beds of one observed section with those of 

 another. The topographical features of the country also aided in work- 

 ing out the structure. A complete publication of all the evidence would 

 have been more costly than perhaps at present desirable, and certainly 

 more so than the funds at hand would permit ; but it is hoped that the 

 map and cross-sections just now about to be published will be found to 

 contain enough of the facts to be fully convincing of the substantial accu- 

 racy of the results. The map was taken in hand by the lithographer over 

 a year ago, and its publication is now almost daily expected, and may 

 take place before this paper can be printed ; so that it is not necessary to 

 give here a map or sections of the Pennsylvania portion of the New 

 Red. 



The survey, then, has shown that the so-called New Red in Montgom- 

 ery county is at least some 27,000 feet thick, and that it may be divided 

 into five parts as follows, from above downwards : shales mostly soft and 

 red, at Pottstown and northeastward, about 10,700 feet thick ; shales, in 

 great part hard and green, partly blackish, and dark red, at the Perkasie 

 tunnel and near it, with some small traces of coal, about 2000 feet ; shales, 

 mostly soft and red, at Lansdale and near it, about 4700 feet ; shales, in 

 great part hard, dark or greenish gray, and blackish, partly dark red, at 

 the Gwynedd and Phcenixville tunnels, with traces of coal, about 3500 

 feet ; shales, mostly soft and red, but in small part dark gray, or green, 

 or blackish, with some beds of brown sandstone and of gray sandstone and 

 pebble rock, at Norristown and eastward, about 6100 feet. That is, in the 

 main, two sets of hard dark shales, with soft red shales above and below 

 •each ; and the lower set of dark shales thicker, blacker and more carbona- 

 ceous than the upper one. Nevertheless, the resemblance of the two sets 

 and the fact that, owing to the great fault, both occur twice near the Dela- 

 ware have occasioned some confusion. It would probably be fruitless to 

 attempt at present outside of Bucks and Montgomery counties to identify 

 more definite horizons than these five great bodies of rock ; and it must 

 still be only with more or less of conjecture that even they can be traced 

 into distant States by the maps and descriptions that have been pub- 

 lished. 



Even in Pennsylvania, outside of those two counties, the published 

 information is too defective for the purpose. If the State government had 

 ever made possible a topographical survey of the whole field, it might 

 probably be comparatively easy now to trace each subdivision by the help 

 of the topography all the way to the Maryland line. As it is, we can 

 only conjecture roughly the horizons of the fossils that have been found. 

 For example, it is very probable that the vertebrate fossils near Emigs- 



