ADDRESS. Ixxvii 
the microscope to particular tissues and particular classes, chiefly due, in 
this country, to the counsels and example of the Microscopical Society of 
London. 
A very interesting application of the microscope has been inade to the 
particles of matter suspended in the atmosphere ; and a systematic continuation 
of such observations by means of glass slides prepared to catch and retain 
atmospheric atoms, promises to be productive of important results. 
We now know that the so-called red-snow of Arctic and Alpine regions is a 
microscopic single-celled organism which vegetates on the surface of snow. 
Cloudy or misty extents of dust-like matter pervading the atmosphere, 
such as have attracted the attention of travellers in the vast coniferous 
forests of North America, and have been borne out to sea, have been found 
to consist of the ‘pollen’ or fertilizing particles of plants, and have been 
called ‘ pollen showers.’ 
M. Daneste*, submitting to microscopic examination similar dust which 
fell from a cloud at Shanghai, found that it consisted of spores of a confervoid 
plant, probably the Trichodesmium erythreum, which vegetates in, and im- 
parts its peculiar colour to, the Chinese Sea. 
Decks of ships, near the Cape de Verd Islands, have been covered by such 
so-called ‘showers’ of impalpable dust, which, by the microscope of Ehrenberg, 
has been shown to consist of minute organisms, chiefly ‘ Diatomacez.’ One 
sample collected on a ship’s deck 500 miles off the coast of Africa, exhibited 
numerous species of freshwater and marine diatoms bearing a close resem- 
blance to South American forms of those organisms. Ehrenberg has recorded 
numerous other instances in his paper printed in the ‘ Berlin Transactions ;’ 
but here, as in other exemplary series of observations of the indefatigable 
- microscopist, the conclusions are perhaps not so satisfactory as the well- 
observed data. 
He speculates upon the self-developing power of organisms in the atmo- 
sphere, affirms that dust-showers are not to be traced to mineral material 
from the earth’s surface, nor to revolving masses of dust material in space, 
nor to atmospheric currents simply ; but to some general law connected with 
the atmosphere of our planet, according to which there is a ‘ self-development’ 
within it of living organisms, which organisms he suspects may have some 
relation to the periodical meteorolites or aérolites. The advocates of pro- 
gressive development may see and hail in this the first step in the series of 
ascending transmutations. The unbiassed observer will be stimulated by the 
startling hypothesis of the celebrated Berlin Professor to more frequent and 
regular examinations of atmospheric organisms. Some late examinations 
of dust-showers clearly show them to have a source which Ehrenberg has 
denied. Some of my hearers may remember the graphic description by 
Her Majesty’s Envoy to Persia, the Hon. C. A. Murray, of the cloud of 
impalpable red dust which darkened the air of Bagdad, and filled the city 
* Annales des Sciences Naturelles, sér. 4. Botanique, t. i. p. 81. 
