PLATE XXVI. 

 Fig. a. 



(Sp. No. 32541. Without analyzer, x 18.) 



Fine-grained ainygdaloidal basalt. The only recognizable original constituent in the ground- 

 mass is the feldspar iu miorolites which most commonly fringe out at the ends. They are not infre- 

 quently arranged iu sheaf-like aggregates. These are best seen with high-power objectives. The 

 major portion of the groundmass consists of a fine felt of chlorite, with minute grains of epidote. It 

 is considered to have resulted from the alteration of a vitreous base. The amygdules consist of calcite. 

 (Described, p. 99.) 



Fig. B. 



(Sp. No. 32541. Without analyzer, x 35.) 



Portion of section from which iig. A was taken viewed with a high power. In this the sheaf-like 

 aggregates of feldspar can be seen. (Described, p. 99.) 



