147. 20. aqua regia: "royal water," so called because it
dissolves gold, is a mixture of nitric and hydrochloric acids.
150. 15. Golconda: a ruined city of India, once famous as a
place for the cutting and polishing of diamonds; used figuratively in
the sense of a mine of wealth.
150. 30. Read Poe's article on "Cryptography," included in his
collected works.
151. 13. Spanish main: that part of the Caribbean Sea adjacent
to the coast of South America. It was part of the route of Spanish
merchant vessels between Spain and her new-world possessions, and was
infested with pirates.