ROGERS, GEOLOGY OF THE CORTLANDT SERIES 17 



rocks. 14 He here states that the emery may be referred with certainty to 

 contact action on pre-existent material, apparently abandoning his former 

 view. In studying the other contact effects, he concentrated on several 

 linear sections, in the first two of which he describes the succession from 

 ordinary mica schist to the same rock carrying sillimanite, then to a rock 

 composed of sillimanite, mica and garnet, and finally to a garnetiferous 

 mica diorite. Analyses show that the change in the schist is in the direc- 

 tion of an increased alumina and iron content as the massive rocks are 

 approached. In the last section of the massive rocks on the limestone, he 

 finds that lime-bearing hornblende and pyroxene are formed along the 

 contact. He finally compares the effects hers with those in several Euro- 

 pean localities, showing that a larger number of" contact minerals is found 

 in the Cortlandt than anywhere else. The contact effects were thus shown 

 to be well developed, a point which will be reverted to in the discussion of 

 the genesis of the emery. 



James F. Kemp, 15 in 1888, described the Eosetown extension of the 

 series; he had also been over the main area under the guidance of Pro- 

 fessor Williams. This smaller body lies about a mile west of Stony Point 

 and is itself about three quarters of a square mile in extent. It is sur- 

 rounded by gneiss and encloses a small patch of marble. The rocks them- 

 selves are all diorites, no hypersthene or olivine having been found in 

 them. Green augite occasionally assumes importance, but in the main it 

 is subordinate to the brown and green hornblende. Emery, similar to 

 that found in the main area, oecurs in these rocks. There is very notice- 

 able contact action along the borders, and numerous dikes radiate out 

 into the surrounding rocks. Six analyses are given in connection with 

 the petrographic description, three of the rocks and three of isolated 

 minerals. 



William H. Hobbs 16 has described the Connecticut extensions of the 

 series in an article which unfortunately is not particularly well known. 

 Two areas were found by him in the crystalline upland of western Con- 

 necticut, which resemble the original Cortlandt area both in the abun- 

 dance of norites and in the elaborate magmatic differentiation; these 

 constitute the northeasterly extension of the Cortlandt. 



The Prospect Hill area, which is the larger and more important of the 

 two, covers about 40 square miles in the township of Litchfield, although 



u "Contact Metamorphism produced in the adjoining Mica Schist and Limestone by 

 the Rocks of the Cortlandt Series," Amer. Jour. Sci., (3), XXXVI, 254. 1888. 



15 "On the Rosetown Extension of the Cortlandt Series," Amer. Jour. Sci., (3), 

 XXXVI, 247. 1888. 



16 Festschrift zum siebzigsten Geburtstage von Harry Kosenbusch, p. 25, Stuttgart. 

 1906. 



