392 Scientific Intelligence. [May, 



gradually filled up by the accumulation of sand and earth, either 

 deposited by the tide, or washed down from the higher ground, 

 and that a chalybeate spring issues from a rock at the upper part 

 of the valley. If, therefore, we may be permitted to suppose 

 that the remains of marine animals were mixed with the clay and 

 sand by which the bay was filled up, we have on the spot both 

 the constituents of the phosphate of iron. 



VIII. Luminosity of the Ocean.* 



After passing Cape Palmas and entering the Gulf of Guinea, 

 the sea appeared of a whitish colour, growing more so until 

 making Prince's Island, and its luminosity also increasing, so 

 that at night the ship seemed to be sailing in a sea of milk. In 

 order to discover the cause of these appearances, a bag of bunt- 

 ing, the mouth extended by a hoop, was kept overboard, and in 

 it were collected vast numbers of animals of various kinds, par- 

 ticularly pellucid salpa, with innumerable little crustaceous 

 animals of the scyllarus genus attached to them, to which I think 

 the whitish colour of the water may be principally ascribed. Of 

 cancers, we reckoned 12 different species, eight having the shape 

 of crabs, and five that of shrimps, and none more than a quarter 

 of an inch in length ; among them the cancer fulgens was con- 

 spicuous. In another species (when put into the microscope by 

 candle light) the luminous property was observed to be in the 

 brain, which, when the animal was at rest, resembled a most 

 brilliant amethyst about the size of a large pin's head, and from 

 which, when it moved, darted flashes of a brilliant silvery light. 

 Beroes, beautiful holothurias, and various gelatinous animals, 

 were also taken up in great numbers. Indeed the Gulf of 

 Guinea appears to be a most prolific region in this sort of 

 animals ; and I have no doubt but the marine entomologist 

 would here be able to add immensely to this branch of natural 

 history. As it was found impossible to preserve the far greater 

 part of these animals, by reason of their delicate organization, 

 the spirit of wine dissolving some, and extracting the colours of 

 others, and as most of them require the aid of a microscope to 

 describe them, a great portion was lost upon us, from the want of 

 a person either to describe or draw them from that instrument. 



Professor Smith, in describing the same part of the Atlantic, 

 observes, that the number of flying-fish is immense. " Shoals 

 of them constantly surrounded the vessel, and at night they give 

 out a white light resembling that of the moon, when reflected by 

 the sea. It was also chiefly at night that we were enabled to 

 catch with the net the greatest number of mollusca and Crustacea. 

 Many different substances contribute to make the surface of the 

 sea light. Some parts of the bodies of most of the Crustacea 

 have certain glittering points, and two or three species of craba 

 were perceived to give out the most brilliant fight. The points 



* Extracted from Tuckey's Narrative of the Expedition to the Zaire. 



