70 ON THE COLORATION OF THE CHINA SEA. 



pletely. " It is," he* says, " an olive-green powder, the grains 

 of which adhere to one another like the substances which remain 

 on a filter, and mixed with filaments resembling hairs, of two 

 kinds, some black, others white and thicker. Under the 

 microscope, it is evidently a mass of very short filaments or 

 fibres, transparent, white, black, and brown, with some spi- 

 cules, reddish, sharp, and with grains of quartzose, transparent 

 sand, adherent between them." 



With some chemical tests the author recognised in this 

 dust the existence of an alkaline salt of silex, and he obtained 

 a small quantity of ammonia by its combustion. He came to 

 the conclusion that it was formed of animal matter with very 

 fine fibres, impregnated with an alkaline salt, probably car- 

 bonate of soda, and containing some grains of quartz. After- 

 wards observing this sand with a more powerful microscope, 

 he recognised that these fibres were vegetable structures, and 

 that they were Conferva, 



What could be the origin of this dust? Dr. Macgowan 

 thought that it might be formed from volcanic ashes, and that 

 it proceeded from the volcanoes of Japan. But the vegetable 

 nature of this substance is manifestly opposed to this notion. 

 Mr. Piddington also to account for the presence of microsco- 

 pical plants in the sand even offers the following supposition. 

 This sand and the ConfervcB which it contains proceed from 

 the interior of the continent, from the marshes and lakes 

 which are so numerous in certain parts of China, from whence 

 they are transported through the air by whirlwinds. It is 

 true that, during all the duration of the phenomenon, the 

 wind blew from the north-east. But this difficulty disappears 

 when the existence of upper currents of the atmosphere is 

 remembered, which blow in the intertropical regions in an 

 opposite direction to the trade winds, that is to say, from west 

 to east, and in the case in question from the land towards the 

 sea. 



1 do not know what the physicists will think of this theory ; 

 but it is evident that the meteorological phenomenon ob- 

 served by Mr. Bellott can be very easily explained by the 

 observations which form the subject of the present memoir. 

 If the Confervae, or, to speak more exactly, if the Algae of the 

 genus Trichodesmium exist in such great abundance in the 

 China Sea, it can readily be understood how these plants 

 might be carried by the winds, and sustained in the air for a 

 certain time under the form of clouds, and how they would 

 fall during a wind from the north-east, without the existence 

 ol opposite directions of atmospheric currents being necessary ; 

 it is obvious also that these filaments might be impregnated 



