198 Examination of some Atmospheric Dust. [Feb, 



Cape de Verd Islands. There is nothing extraordinary then in sup- 

 posing that this dust was originally raised by some such cause as a 

 great storm or whirlwind, and that it might be carried by the superior 

 current to a very great distance before it fell. It was probably also 

 raised in a very dry state, and one cause aiding its fall might be tha 

 absorption of the humidity of the air as it approached the ocean, hair be- 

 ing highly hygrometric, and hence the difficulty of supposing it to have 

 crossed any great extent of sea, as it must have done to come from Corea 

 or Japan. It is evidently, by Dr. Bellott's description, so light that 

 (which appeared to him very unaccountable), it obeyed strictly, like a 

 part of the atmosphere, the laws which regulate the deposition of dew ; 

 for it was deposited on the guns and other quickly radiating bodies but 

 " would not settle" on his newspaper ! He forgot that the paper, being a 

 non-conductor of the highest order, prevented the radiation from the 

 deck in that part, and thus keeping it at a little higher temperature 

 prevented the depositing of the dew, which in this case was carrying 

 the dust with it. 



It is a startling thing to say, and I do it with all caution, but it is 

 quite within the limits of possibility, if not of probability, that this dust 

 came originally from the steppes of Tartary ! and the presence of an 

 alkaline salt in it is no small addition to the probabilities. The 

 nearest part of Mongolia without the Great Wall is only about 675 miles 

 from Shanghae, a distance to which a light mass, half dust and half fibre, 

 might easily be carried, especially if raised as it would, be there, in a 

 perfectly dry state ; the dry winds of Tartary, and the Pak-fung or 

 dry north wind of China which splits and cracks up in an hour the most 

 seasoned wood work, are well known. 



P. S. — Since this paper was written, the dust has, through the kind 

 assistance of Dr. Cantor and Mr. J. W. Grant, C. S. been examined by 

 much more powerful microscopes than I possess, and these gentlemen, 

 together with Major Munro, pronounce the fibres to be Confervse, and 

 not hair. Some of these bodies may afford the ammonia in combus- 

 tion of which the smell is so strong and distinct as to lead us to sup- 

 pose, without this correction, that the fibres are hair. 



Assuming then these to be Confervas, we have to the North-East- 

 ward as before, Japan and Correa ; and to the Westward and North- 

 Westward the Poyang, Tai-you, Hong-tze and other great inland lakes 



