PLATE XXXIl. 



Fig. a. 



(Sp. No. 23645. Without analyzer, x 35.) 



Perlitic parting in a fragment from a basalt tuff. The perlitic cracks are marked hy accumu- 

 lations of epidote grains. The remainder of the fragment consists of au exceedingly fine chlorite 

 felt, with here and there a small feldspar microlite embedded in it. This was probably a fragment of 

 basalt glass. (Described, p. 138.) 



Fig. B. 



(Sp. No. 23646. Without analyzer, x 35.) 



Photomicrograph of a section of basalt tuff. The illustration shows the sickle-shaped bodies 

 which are characteristic for the fine eolian-deposited volcanic ejectamenta. (Described, p. 142.) 



