1847.] Examination of some Atmospheric Dust. 199 



of China, some or most of which are shallow (jheels ?) and might 

 furnish vast quantities of remains of confervse on their inundated 

 banks and flats. 



In a paper by Mr. Darwin in the Journal of the Geological Society for 

 1845, on the fall of the Fine Dust in the Atlantic, which had escaped 

 my notice and which Mr. Laidlay has been good enough to point out 

 to me, mention is made not only of small but of coloured parti- 

 cles of stone 10 1 00 th of an inch square, with some few a little larger, and 

 much fine matter ; but all the dusts examined by Mr. Darwin fuse 

 under the blowpipe. Professor Ehrenburg finds that this dust contained 

 no less than sixty-seven forms of Infusoria, that is of their siliceous 

 tissues, but none of the soft parts remain. We may observe too that 

 the whole of the dust falling on the Eastern side of the Atlantic comes 

 from the neighbouring shores of Africa. 



