chap, vi.] GEOLOGY. 127 



Janeiro, observed the sea in those parts to be unusually 

 luminous, flashing like lightning. On examining the water 

 he discovered two kinds of animals that occasioned this ap- 

 pearance. The one he called Cancer fulgens, a crustaceous 

 insect ; the other pellucens, a species of Medusa. The former 

 of these somewhat resembles a small shrimp, and light ap- 

 pears to issue from every part of its body. The latter, 

 which is the most luminous of all zoophytes, measures about 

 six inches across ; its central part is opaque, and from it de- 

 pend several long tentacula. Numerous other reasons have 

 been given for the luminosity of the ocean, which has 

 been deemed phosphoric by some, and electrical by others. 

 Macartney, Humboldt, and many others have entered at 

 length into a discussion on this subject. Humboldt says 

 that " the luminous appearance of the sea is due partly to 

 living animals, and partly to organic fibres and membranes 

 derived from the destruction of these living torchbearers." 



GEOLOGY. 



The first description of the geology of Madeira which I 

 have met with is contained in the posthumous work of 

 Bowdich, a traveller whose name belongs to the list of those 

 that have fallen victims to an ardent zeal for science, and who 

 died, soon after quitting Madeira, under the burning suns of 

 Ashantee. In this work, published by his widow, who nobly 

 accompanied him on the hazardous enterprise in which he 

 perished, there is a general account of the eruptive rocks 

 of which the island chiefly consists, and there is mention also 

 of a stratified limestone, near S a .° Vincente, to which his at- 

 tention was directed by Mr. Veitch. The highly-inclined 

 position and crystalline character of this calcareous rock led 

 Mr. Bowdich to regard it as tbat which some geologists have 



