16 ANNALS NEW YORK ACADEMY OF SCIENCES 



railroad. A glance at the map suffices to show the incompleteness of his 

 knowledge as regards the distribution. He discusses first norite proper; 

 then hornblende norite, mica norite, augite norite and finally pyroxenite. 

 Under mica norite, he describes the "Butler Section," a cliff in which 

 norite proper, augite norite and other rocks are arranged in layers. He 

 ascribes it to ordinary metamorphism. This and similar cases have been 

 described by the present writer 11 and will be discussed in the paper here 

 contributed. Williams states also in this paper that the emery is a segre- 

 gation in the norite and discusses in this connection the composition of 

 the ore as compared with that of Konsperg, Bohemia. In a later note, 12 

 he gives an analysis of the orthoclase of these rocks, which removes the 

 suspicion that it may be merely unstriated plagioclase. 



Williams's third paper 13 is on the gabbros and diorites. He states that 

 the gabbro is a rather rare rock ; but adds that it always shows metamor- 

 phism and always occurs adjoining the limestone, therefrom deducing the 

 fact that it is a hybrid formed by the action of the norite magma on this 

 latter rock. He divides the diorites into hornblende and mica diorite. 

 Under the caption hornblende diorite, he describes in turn brown horn- 

 blende diorite, hornblendite, green hornblende diorite and mica horn- 

 blende diorite. He subdivides mica diorite into mica diorite proper, 

 hornblende mica diorite, hypersthene mica diorite and quartz mica diorite. 

 In concluding, he states that the series is due to long-continued igneous 

 action, different types being successively produced which broke through 

 those already solidified, the more acid types apparently appearing last. 



This concludes his petrographic study, and notwithstanding the incom- 

 pleteness of his knowledge of the distribution and extent of the types, his 

 work stands as a well-rounded and scholarly investigation. His nomen- 

 clature is particularly felicitous ; in a district of such multifarious differ- 

 entiations, the free use of mineral prefixes is preferable to the adoption 

 of a number of new terms. It is greatly to be regretted that Professor 

 Williams's untimely death prevented the further prosecution of his work 

 in the district; a complete study of the magmatic differentiation in the 

 Cortlandt Series would have been indeed valuable from a petrologist of 

 his experience and perspicacity. 



Consonant with his original plan, having completed his study of the 

 igneous rocks themselves, he describes their effect on the surrounding 



11 "Original Gneissoid Structure in the Cortlandt Series," Amer. Jour. Sci., (4), XXXI, 

 125. 1911. 



™Op. cit., p. 243. 



13 "Gabbros and Diorites of the Cortlandt Series," Amer. Jour. Sci., (3), XXXV, 438. 

 1888. 



