RARE 
Figure 1.—Diabase, upper surface of intrusive Figure 2.—Basalt; porphyritic phase near base 
sheet, x 15. Crossed nicols. of extrusive sheet, x 10. Crossed nicols. 
Figure 3. —Basalt, with calcite-chlorite amyg- Figure 4.—Basalt glass, with steam-bubble 
dule, from “datolite zone," x то. Ordi- cavities; upper surface of extrusive sheet, 
nary light. ° x 10. Ordinary light. 
