232 BULLETIN OF THE 



syenite type. These analyses were made by Dr. W. H. Melville in tlie 

 laboratory of the United States Geological Survey at Washington. For 

 comparison, Analyses I. of Theralite/ II. EliBolite-syenite ^ (" grnv 

 granite," Fourche Mountain, Arkansas), and III. Acmite-trachvte ^ 

 (from the Klihlsbrnnnen Siebengebirge, Germany), are introduced for 

 comparison : — 



100.00 99.50 99.67 99.56 99.39 99.56 99.09 



Comparison with other Aanite-trachijtes. — In chemical and mineralogi- 

 cal composition and habitus, the fine-grained rocks are almost identical 

 with the classical acmito-trachyte from the Kiihlsbriinnen in the Sie- 

 bengebirge. The microscopic characters of the German rock are given 

 in Rosenbusch, (Mik. Physiog., Vol. II. p. 599,) where it is stated that 

 the rock, when weathered, is filled with peculiar round pores, which do 

 not exist in the fresh rock, but are there represented hj areas of a 

 brownish yellow isotropic, or partly cryptocrystalline substance, which 

 is occasionally developed in radially built spherulites of positive charac- 

 ter, a single spherulite occupying the space of a subsequent cavity. In 

 slides from a vei'y fresh specimen of the German rock collected by one 

 of the writers, the yellowish brown color of these areas is very faint or 



1 J. E. Wolff, Petrography of tlie Crazj- Mountains, 1885. 



2 Williams, he. cit., p. 81. 



•' G. Bischof, in Von Declicn's Geogn. Besclir. d. Siebengebirges. Ver. d. Preuss. 

 Uli. und West., VA IX p 310. 



