384 Professor Owen's Address; 



similar dust which fell from a cloud at Shanghai, found that it 

 consisted of spores of a confervoid plant, probably the Trichodes- 

 mium erythrceum, which vegetates in, and imparts its peculiar 

 colour to the Chinese Sea. Decks of ships, near the Cape de 

 Verde 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 " Diatomacese." 

 One sample collected on a ship's deck 500 miles oif the coast of 

 Africa exhibited numerous species of freshwater and marine diatoms 

 bearing a close resemblance to South American forms of those organ- 

 isms. 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 miscroscopist, the conclu- 

 sions are perhaps not so satisfactory as the well observed data. He 

 speculates upon the self-developing power of organisms in the 

 atmosphere,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, accord- 

 ing 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 aerolites. The advocates of 

 progressive development may see and hail in this the first step in 

 the series of accending transmutations. The unbiassed observer 

 will be stimnlated 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 with a panic. The specimen he collected was 

 examined by my successor, at the Royal College of Surgeons, Prof. 

 Quekett, and that experienced microscopist could detect only 

 inorganic particles, such as fine quartz sand, without any trace 

 of Diatomacese or other organic matter. Dr. Lawson has obtained 

 a similar result from the examination of the material of a showers 

 of moist dust or mud which fell at Corfu, in March, 1857 : it consisted 

 ' for the most part of minute angular particles of a quartzose sand. 

 Here, therefore, is afield of observation for the miscroscopist, which 

 has doubtless most interesting results as the reward of persevering 

 research. 



