66 Canadian Record of Science. 



some extent. It is slightly pleochroic, the absorption 

 ranging from colorless to pale yellow. The cleavage is 

 good, and the extinction along cc P co is 44°. The horn- 

 blende occurs as a few large irregular individuals, and in 

 numerous small idiomorphic ones. The pleochroism varies 

 from deep brown to pale yellow. The extinction along 

 cc p x is 22°. 



Apatite in long slender needles and idiomorphic basal 

 sections, is well represented. The ground mass consists 

 of a finely granular aggregate of the ferro-magnesian 

 constituents, but there is, in addition, a very large amount 

 of isotropic material. This is colorless, cpuite allotrio- 

 morphic, and has a low index of refraction. Heated with 

 hydrochloric acid, it gelatinizes. It is optically similar to 

 the analcite in the cavities, but whether it is primary or 

 secondary it is impossible to state. l 



The analcite in the cavities is secondary, and in many 

 cases has crystallized out, showing the outline of the 

 tetragonal trisoctahedron. It occasionally is feebly doubly 

 refracting. 



The rock is evidently an olivine — free analcite basalt 

 which corresponds to the Fourchites 2 of J. F. "Williams. 



1. The Monchiquites or Analcite Group of Igneous Hocks, by L. V Firsson. Jour, of 

 Geol., Vol. IX., No. 6, 1896, p. 679, et seq. 



2. Igneous Rocks of Arkansas. Rep. of Geol. Survey, 1890, p. 11U. 



