Frazer.l 410 [Dec. 4, 1885. 



many sections across the crystalline rocks of the South mountain and 

 the hills and plains of Adams, York, Lancaster and Chester counties, 

 with the evidence they contain of the pre-Palseozoic age of these 

 rocks, which were published in Vols. C, CC and CCC, and Ihe part 

 of C 4 which Prof. Lesley has permitted to appear as it was written, 

 are easier to ignore than to invalidate. It is not necessary to characterize 

 the conduct of authors who, professing to discuss a subject in the interest 

 of truth, and filling pages of their books, as well as parts of their index, 

 with unjust imputations on the truthfulness and reliability of a geo- 

 logist whose services to his science are recognized throughout the world, 

 give an example of their own possession of this virtue by suppressing all 

 that does not happen to coincide with their own peculiar views, but which 

 (to compensate for this) forms by far the larger part of the literature on 

 the subject. Profs. Whitney and Wadsworth quote Mr. C. E. Hall's 

 paper in the Am. Phil. Soc.'s Proc. of 1880, but do not allude to the 

 criticism of those views in the A. P. S.'s Proc. for Dec, 1882, nor even 

 quote their author's summary of his maturer views printed in part of C 4 . 

 In the criticism of the views expressed in C 6 (which are virtually the same 

 as those read before the A. P. S. and quoted at length) the author was 

 supported at the time by Prof. Lesley (see "The Horizon of the South 

 Valley Hill rocks in Pennsylvania"), and the structure on which he based 

 his argument had received the endorsement of Profs. Gosselet and Barrois 

 on the assumption of the facts of dip, &c, about which there was no dis- 

 pute. Thesection at "Gulf Mills," on which Mr. Hall relied (C 6 . p. 32) for 

 his structure, is shown in the above paper, where it is independently given, 

 to have been so drawn by Mr. Hall that eveiy synclinal is in reality an 

 anticlinal and vice versa, and this is confirmed by a later section pub- 

 lished in the transactions of the A. A. A. S. of the Philadelphia meeting 

 in 1884. Further information on this subject may be found in the "Theses 

 presentees a la Faculte des Sciences de Lille," "Reply to a paper entitled 

 Notes on the Geology of Chester county and vicinity" (Journal of the 

 Franklin Institute, April, 1884) and "Review of C 4 " (American Natural- 

 ist, October, 1883). by the writer. 



Those who would discuss the Archaean of Southeastern Pennsylvania 

 without reference to the lessons to be learned from the South mountain 

 in Franklin, Cumberland, Adams and York counties, or the great flat 

 Tocquan anticlinal of Southwestern Lancaster are incompetent to do so 

 either from ignorance of the facts or from a disingenuous desire to sup- 

 press them. 



