ASCENSION.
Basaltic lavas.--Numerous craters truncated on the same side.--Singular structure of volcanic bombs.--Aeriform explosions.--Ejected granite fragments.--Trachytic rocks.--Singular veins.--Jasper, its manner of formation.--Concretions in pumiceous tuff.--Calcareous deposits and frondescent incrustations on the coast.--Remarkable laminated beds, alternating with, and passing into obsidian.--Origin of obsidian.--Lamination of volcanic rocks.