1891.1 [Lesley, 



color of the surface of the ground contrasted with the red on either side 

 from the several thousand feet of red shales above and below, except 

 where trap replaces them above for a long distance from the Haycock 

 southwestward. The geological structure is also well shown by very nu- 

 merous observed dips and strikes. 



Here and there among the harder beds, exposures have been observed 

 of a couple of blackish shale layers some three feet thick, perhaps identi- 

 cal with those of the boring. One was seen by the roadside near Rufe's 

 Corner ; two in a ravine a mile and a half north of Ottsville, where some 

 digging was done half a dozen years ago in a vain search for coal of any 

 economical value, though small traces of it appear to have been found ; 

 another exposure of blackish shales was seen half a mile west of Perkasie ; 

 and still another about a mile east of Harleysville. 



It is, of course, extremely improbable that the beds with a known out- 

 crop of about sixty miles in length, cut across by numerous streams and 

 roads and by several railroads and even in great part by a tunnel, and fa- 

 miliar throughout every foot of its surface to the highly observant inhabi- 

 tants of the country, could have a coal bed of any value that should 

 never, until this well, have been discovered through any complete natural 

 exposure or through an occasional very noticeable outcropping or blos- 

 som. Indeed, facts observable on the surface, such as measured rock ex- 

 posures, combined with proper regard to their dips, strikes and relative 

 position and elevation, could no doubt give a very complete section of all 

 the beds pierced by the well ; and perhaps that will prove to be possible 

 even with the somewhat rough collection of materials already made. 

 From such observations on the surface, the character and thickness of 

 each bed is to be known far more precisely and thoroughly than could be 

 possible from any boring however careful, and beyond all comparison 

 with the results of an ordinary one. The difficulty of accurate informa- 

 tion from such wells is shown by the doubt in the present case whether 

 the so-called coal bed was nine feet in thickness or five and a half. 



The well record, in spite of all the imperfections that must be expected, 

 has value as giving for a great thickness of rock beds a connected view 

 that may serve in some degree as a check upon the not very essential er- 

 rors that might arise in combining surface observations, especially those 

 rough ones hitherto obtained. But the chief importance of the record is 

 perhaps as an illustration of how ready men are to lay out thousands of 

 dollars for such explorations where the same number of hundreds would 

 by a surface survey give fuller and more accurate information. 



PROC. AMER. PHILOS. SOC. XXIX. 135. D. PRINTED MAY 14, 1891. 



