Note 2 — Chapter II · FERNANDO NORONHA; TERCEIRA; TAHITI, ETC.
Reading edition
MacCulloch, however, has described and given a plate of (“Geolog. Trans.” 1st series, vol. iv, p. 225) a trap rock, with cavities filled up horizontally with quartz and chalcedony. The upper halves of these cavities are often filled by layers, which follow each irregularity of the surface, and by little depending stalactites of the same siliceous substances.