What are volcanic rocks? Lava? Scoriæ? Pumice-stone?
How is the vesicular structure produced?
What are volcanic breccias? Volcanic grits?
What is the composition of the trappean rocks?
What is the amygdaloidal structure?
What are the three varieties of trappean rocks, and how are they distinguished?
Fig. 1.
Name the stratified rocks. Describe gneiss. Mica slate. Sandstone. Conglomerate. Greensand. Describe the varieties of limestone.