

LETTER OF TRANSMITTAL. F*. xi 



An interesting feature of this report is the description 

 which Prof. Claypole gives of the trap dykes of the Cove. 

 Dr. Henderson's long dyke assumes a new aspect ; and im- 

 portant conclusions may be drawn from the fact that four 

 parallel dykes traverse the Cove, one of which crosses Cum^ 

 berland county southward, and another projects itself 

 northward beyond Halifax, in Dauphin county. The trend 

 of these evidently profound cracks in the earth crust is 

 diagonal to the middle radius of the concentric circular 

 segments produced by the thrust already mentioned. 



Prof. Claypole' s researches in Perry county in 1882 and 

 1883 have resulted in important modifications of the know- 

 ledge obtained by previous surveys, especially in the fol- 

 lowing particulars : — 



1. The limitation of the name Clinton to the lower divi- 

 sion of that mass of shales and thin sandstones numbered 

 V by the First Survey, no Clinton fossils having been 

 found in the upper division. 



2. The consequent establishment of the Onondaga form- 

 ation, as embracing the upper 1600 feet of No. Y, partly 

 on stratigraphical and partly on palseontological grounds. 



3. The demonstration of the absence of Niagara beds 

 from No. Y. 



4. The demonstration of the absence of the Comiferous 

 limestone group from the whole county, and the allotment 

 of the strata hitherto considered as representing that group 

 to the Marcellus subdivision of the Hamilton division of 

 No. YIII. 



5. The definition of 600 or 700 feet of shales, chiefly by 

 their fossil forms, as Upper Hamilton, Genessee and Port- 

 age beds. 



6. The demonstration of a fauna, partly Chemung, and 

 partly peculiar, high up in the Catskill formation No. IX, 

 and — 



7. The systematic tracing of the richly fossiliferous 

 Kingsmill sandstone along all the Catskill outcrops of the 

 county. 



The proofs of these propositions will be given in detail 

 in the second part of his report. 



