176 NEW YORK STATE MUSEUM 



known local geologist, was made one of the assistant geologists of the 

 first geological district of this State.^ Dr Horton encountered the 

 same difficulty in determining the dip of the Trilobite mountain beds 

 that all later observers have had, namely a tendency to confound 

 cleavage and bedding. He says that the Trilobite mountain strata 

 " repose unconformably upon the Millstone grit (Shawangunk grit) 

 at the western base of Shawangunk mountain. "^ Qn the next page, 

 however, he hesitates and says that this southeast dip is " far from 

 certain. The stratification is to me still uncertain." 



Several years later, W. W. Mather, geologist in charge of the first 

 district, published his report where we find that he reached more 

 definite conclusions. Speaking of the Manlius and Helderbergian 

 series, he says " These limestones dip in a west to northwest direc- 

 tion, lying upKDn the subjacent Shawangunk rocks conformably; but 

 some of the strata are rather enigmatical and appear to dip to the 

 east-southeast in consequence of the cleavage or shivering of the 

 strata since their deposition. In some of the strata the real dip is 

 evident, but in others it is not, and it was only after minute examina- 

 tion that the real direction was with certainty determined."^ 



Dr S. T. Barrett of Port Jervis gave in 1876^ the result of many 

 years detailed work on the rocks of this region. He correlated the 

 strata with those farther north and west in New York State, giving 

 the horizons and thicknesses from bottom to top as follows : 



Feet 



1 Tentaculite limestone '. 20 



2 Favosites limestone 2-5 



3 Lower Pentamerus and Cherty 40 



4 Delthyris shale 120 



5 Upper quarry 10 



6 Upper shale 150 



7 Trilobite layers 5-10 



8 Oriskany and Cauda Galli 500-800 



'N. Y. Geol. Rep't ist dist. 1839. p. 135. 

 'N. Y. Geol. Rep't ist dist. 1839. p. 150. 

 'Geol. N. Y. ist dist. 1842. p. 332. 

 *N. Y. Lye. Nat. Hist. 11:290. 



