FEWER, THE WATCHVSG BASALT 183 



from many localities.^^ In nearly all cases, they agree with that which 

 the author has determined for the Watchung series. 



Breithaiipt arrived at certain well-founded conclusions regarding the 

 conditions of formation of zeolites,^'* as follows : 



It is notable that it (that is, their formation) occurs not only in the younger 

 eruptive rocks, in whose bubble cavities the zeolites are especially at home, 

 . . . but also in much older varieties of rock. But where the zeolites also 

 appear, they can be observed as always only products of leaching, and have 

 depended upon lateral secretion, and herein they accord perfectly with the 

 occurrences in bubble-cavities. The bubble-cavities, as well as the veins in 

 which they appear, are mostly wholly free from magnesia or iron-oiide con- 

 taining minerals ; at the most, only traces of these ingredients occur, whose 

 nonexistence is related to the mineralogical-chemical character of the zeolites. 



In a recent article appearing in the Annals of the New York Academy 

 of Sciences, vol. xix, pp. 131-134, 1909, W. G. Levison has recorded his 

 observations on the sequences of the minerals of the Newark igneous 

 rocks at various New Jersey localities. His results indicate that he 

 found no fixed order in the sequence in which the minerals appeared 

 even in specimens from the same locality. His work, however, was done 

 without the aid of the microscope. The present writer's investigations 

 have indicated that replacement phenomena in these rocks have followed 

 such a course that it is hardly possible to reach satisfactory conclusions 

 from macroscopic observations alone. 



As a final citation, which bears upon both the sequence of deposition 

 and the general nature of the process, Brogger's well-known paper on 

 "Die Mineralien der Syenitpegmatitgange der Siidnorwegischen Augit- 

 Nephelinsyenite" °^ is so interesting and instructive that the writer de- 

 sires to quote certain parts at considerable length. 



Brogger takes up the geological relations in the following order: 



1. Phase of magmatic consolidation. 



2. Chief phase of the pneumatolytic minerals. These are rich in 

 fluorine, boron and sulphur, whose derivation he ascribes to the magma. 



3. Phase of zeolite formation. 

 Eegarding this phase, he says in part : 



Under the continued cooling of the veins and their surroundings, the condi- 

 tions of mineral formation must by degrees change more and more: finally the 

 pneumatolytic exhalations, which at first must have consisted principally of 

 fluorine, chlorine and boron-rich combinations, then of sulphurbearing combi- 



59 Op. cit., pp. 103-107, 260-261. 



™ Op. cit.. p. 259. 



" Zeitschr. f. Kryst. und Min., vol. 16, 1890. 



