68 ON THE COLORATION OF THE CHINA SEA. 



imperfect as it necessarily was, owing to my having only 

 fragments more or less altered at my command, has not left 

 a doubt as to their genuine nature. I found in them directly 

 all the characters assigned to the genus Trichodesmium by 

 MM. Ehrenberg and Montagne. The determination of the 

 species was more difficult. These plants resembled greatly 

 Tricliodesmhun erythrceurti ; but I should not have been able 

 to assure myself on this point, had not M. Montagne, whose 

 authority on these subjects is so great, and who had kindly 

 observed my Algae under the microscope, changed my pre- 

 sumption into certainty. 



From this fact, I could no longer doubt that the remarkable 

 phenomenon of the microscopical vegetation in the Red Sea 

 is also presented in the China Sea ; and that true minute Algse 

 are the cause of the strange coloration which certain parts of 

 that sea exhibit. 



I wished to know if this fact had been already observed, 

 and after many fruitless researches, I at last met with a very 

 curious observation, which made me presume that these little 

 plants had been already noticed, although the observers had 

 mistaken their nature, and especially their origin. As this 

 observation is very interesting in many respects, I shall ven- 

 ture to give it with some details. It is the chemical and 

 microscopical examination of some sand which fell from a 

 cloud at Shanghai, made by Mr. Piddington, Curator of the 

 Museum of Economic Geology of India. It is published in 

 the Journal of the Asiatic Society of Bengal (1846). 



This sand had been collected by Mr. Bellott, surgeon to 

 H. M. S. " Wolf," and was transmitted by him to Dr. Mac- 

 gowan, physician to the hospital at Ningpo, who in his turn 

 forwarded it to the Asiatic Society of Bengal. 



Mr. Bellott's letter is as follows : — 



" H. M. 8. ' Wolf; Shanghcn, March 16, 184G. 

 " My dear Sir, 



" I SENT for the account of a shower of fine sand which fell here 

 yesterday, the 15th. The wind was N. N. E., No. 1, rather fresh ; then 

 N, E., No. 2 ; then E. N. B., No. 3 ; and at last N. E. ; and calm at sun- 

 set. A fog was observed, which was regarded as an ordinary fog ; but the 

 officers who were walking on the shore, remarked that their shoes and 

 their trousers were covered with dust. I observed it myself in the after- 

 noon. At 8 o'cloclc in the evening the dust was visible on the guns, the 

 upper works, and other polished surfaces on the deck. I gathered as much 

 of it as I could. In placing the dust upon the finger and raising it in the 

 direction of the sun's rays, which on account of this phenomenon had only 

 lialf their usual brightness, the particles which composed it were bril- 

 liant : although impalpable when held between the fingers aud thumb, 

 the dust caused a gritty sensation between the teeth. The dust passed 

 over the vessel in light clouds, when the wind freshened ; it was some- 



