626 



Report of tup: State Geologist. 



4. 



Rafiriesquma alternata (Con.), H. and C. 



(o) 



5. 



Rafinesquina deltoidea (Con.), H. and C. 



(c) 



6. 



Orthi.s (PhtttjstroplikC) hiforata (Schl.), Bill. 



(a) 



i . 



Orthis (I) alma i hi Id) testvdwnaria, Dal. 



(a) 



8. 



Plectamhonites sericea (Sowerby), II. and C. 



(e) 



9. 



Zygospira recurvirostra, Hall. 



0') 



10. 



. 1 saph us plat yceplial us, Stokes. 



(c) 



11. 



Calymene callicephala, Green. 



00 



12. 



Ceraunis pi e u rexantliemus, Green. 



« 



13. 



Mwchisonia gracilis, Hall. 



(r) 



14. 



Ortlioceras. 





The total thickness of this section from the lowest exposures in the 

 Narrows to the top of the Prospect quarries, as determined by 'the authors 

 with tape and Locke level measurement of the various parts, is 270 feet.* This 

 amount, however, does not give the thickness of the formation, since neither 

 its top nor bottom "is shown at Trenton Falls. The thickness of the same 

 section, as given by Mr. AVhite, is 325 feet,f while Mr. Darton stated : " The 

 greatest development of the Trenton which I have observed is at Trenton 

 Falls, where there appears to be a thickness of 120 feet. 11 % In 1838, Vanuxem 

 said "at Trenton Falls, the thickness is upwards of one hundred feet,"§ 

 though in his final report he simply states that the sides of the gorge are 



* Recently the writer partly remeasured the section using an Abney's level and obtained the same result, 187 feet, for the thic k- 

 Bess of the rocks from the creek level in the Narrows to the top of Mill Dam fall. The thickness of the rocks from the foot of 

 High fall to the top of its lower part, is' sixty-seven and one-half feet; to the contorted layer, eleven and one-half feet more : from 

 the base of the upper part of High fall to its crest, forty-eight feet ; and from that stratum to the top of Mill Dam fall, twenty- 

 two feet. From the foot of the railroad pier, which rests on the top layer of Mill Dam fall, to the base of the massive crystalline 

 limestone, I obtained sixty-two feet, making the total thickness of the section 275 feet. c. s p. 



7 Transactions New York Academy of Science Vol. XV, pp. 79 and 80. On page 89 the total thickness of the upper and 

 middle Trenton limestone at Trenton Falls is given at 336 feet ; while on page 81 it is stated that the total thickness of the typical 

 Trenton Falls section is 318 feet 10 inches. However, in this latter place, if the sixteen feet in the zones repeated in the lower 

 part of the section be omitted, it will leave ten feel six inches instead of " twenty-six feet six inches below D? " as stated by Mr. 

 White. In his later paper on " The Original Trenton rocks " (American Journal of Science, Fourth Series, Vol. I, December. 

 1896, page 430) Mi. White gives 325 feet for the Trenton Falls section. Since the above was written I have received a letter 

 from Mr. While, in which he states that his section w as thirty feet too thick, because he mistook " a blurred 6" in his note 

 book for a 9. He further said that the following corrections should be made on pp. 78 and 79 of his article: 



Total thickness. 

 Feet. 



" D'2-i- 1 , 106 



D 14 , 108J4 



D 1 ^ Bhould read extending to the top of upper portion of High fall, 168 



D 16 , after third fall insert (Mill Dam fall), 188 



D 17 (layer on which pier of It. R. bridge rests), 185 



D>8 188 



D19 191 



D20, 193 



D 2 », for Mill Dam read Alhainbra, 199 



1)2-', 269 



D23, .... 28-1 



After making the above corrections it will be found that the rocks from the base of High fall to the top of Mill Dam fall 

 have nearly the same thickness in both sections, 1811 feet in White's, and 138 feet in that of Prosser and Cumings c. s. p. 

 t Thirteenth Annual Keport State Geologist [New York], 1895, p. 425. 

 {Second Annual Report Third District (Assembly Document, 1838, No. 200), p. 275. 



