GENERAL MEETING. 35 
of volcanic dust and of the theory which ascribes recent meteo- 
rologic phenomena to the dust ejected by Krakatoa. In this Messrs. 
Duron, Pau, W. B. Taytor, Drier, Ropinson, and Warp 
participated. Mr. Durron pointed out that their process of for- 
mation tends to give volcanic dust particles a quasi-definite size, 
and probably does not produce a large amount of dust fine enough 
for indefinite suspension. The greatest distance to which volcanic 
dust has been definitely ascertained to travel is eight hundred miles. 
Mr. Paut argued from the violence of the Krakatoan explosion 
its competence to charge the atmosphere at very great altitudes, 
and considered the fineness of the dust a sufficient explanation of 
its indefinite suspension. 
Mr. Taytor said the phenomenon to be accounted for was 
specially remarkable, first, for the unusual elevation of the finely- 
divided smoke or dust extending far above the highest cirrus clouds, 
or probably to twenty or thirty miles above the earth’s surface (as 
shown by its twilight duration); secondly, for its wide diffusion 
(covering a large fraction of the terrestrial atmosphere); and 
thirdly, for the long continuance of its suspension in the air (ex- 
tending over many months). Mr. Lockyer and Mr. Preece had 
suggested an electrical condition of the matter as favoring both its 
extraordinary diffusion and its equally extraordinary suspension. 
This hypothesis seemed to the speaker very plausible. Electricity 
is a phenomenon of volcanic eruption, and dust particles charged 
with electricity in the same sense with the earth would be repelled 
not only by one another, but by the earth. At thirty miles above 
the ground the air is not only very rare, but is practically anhydrous, 
and the discharge of electricity is impossible. 
Mr. DILLER, in response to a question by Mr. Paul, said that the 
microscope reveals no limit to the fineness of Krakatoan dust. The 
higher the magnifying power applied, the greater the number of 
particles visible; and this relation extends to the limits afforded by 
the capacity of the instrument. To more powerful microscopes, 
yet finer particles would presumably be visible. 
