PLATE XXV. 



Fig. a. 

 (Sp. No. 32116.) 



Pbotograpb, with very slight enlargement, of the polished surface of a very fine grained hut 

 very amygdaloidal basalt. The amygdules are of irregular sliape, hut iu general with a rounded 

 or tubular character. The original cavities have been filled with chlorite and (juartz. The chlo- 

 ritic ainygdules are the most common. A few of the wbito quartz amygdules may be seen on the 

 left-band side of the figure. It should be noted that owing to the softness of the chlorite some of the 

 amygdules have become impregnated with the powder used in poli,shing the specimen. This could 

 not be removed, and in many cases may be seen filling as well as outlining the chlorite amygdules. 

 (Described, p. 95.) 



Pig. B. 



(Sp. No. 32903. Without analyzer, x 18.) 



Photomicrograph of a section of the fine grained, possibly vitreous, amygdaloidal basalt repre- 

 sented in fig. A of PI. XXVII. The amygdules consist of chlorite, quartz, and feldspar. The greatest 

 interest centers in tlie groundmass. This consists of a fine felt of chlorite with minute epidote grains. 

 Traversing this, one sees in places delicate flowage lines. This is believed to represent a once vitreous 

 basalt. (Described, p. 102.) 



280 



