I have already observed that the silvery lustre and frequency of mica have contributed to give Guiana great celebrity for metallic wealth. The peak of Calitamini, glowing every evening at sunset with a reddish fire, still attracts the attention of the inhabitants of Maypures. According to the fabulous stories of the natives, the islets of mica-slate, situate in lake Amucu, augment by their reflection the lustre of the nebulae of the southern sky. "Every mountain," says Raleigh, "every stone in the forests of the Orinoco, shines like the precious metals; if it be not gold, it is madre del oro (mother of gold)." Raleigh asserts that he brought back gangues of auriferous white quartz ("harde white sparr"); and to prove the richness of this ore he gives an account of the assays that were made by the officers of the mint at London.* (* Messrs. Westewood, Dimocke, and Bulmar.) I have no reason to believe that the chemists of that time sought to lead Queen Elizabeth into error, and I will not insult the memory of Raleigh by supposing, like his contemporaries,* that the auriferous quartz which he brought home had not been collected in America. (* See the defence of Raleigh in the preface to the Discovery of Guiana, 1596 pages 2 to 4.) We cannot judge of things from which we are separated by so long an interval of time. The gneiss of the littoral chain* contains traces of the precious metals (* In the southern branch of this chain which passes by Yusma, Villa de Cura and Ocumare, particularly near Buria, Los Teques and Los Marietas.); and some grains of gold have been found in the mountains of Parima, near the mission of Encaramada. How can we infer the absolute sterility of the primitive rocks of Guiana from testimony merely negative, from the circumstance that during a journey of three months we saw no auriferous vein appearing above the soil?