276 THE BEGINNINGS OF LIFE. 



ferent methods. At first he made use of a simple 

 aspirator, though he afterwards worked with the aid 

 of an aeroscope — an instrument which he had himself 

 devised ^^ and by means of which he concentrated upon 

 a space of glass, two millimetres square and moistened 

 with glycerine, all the corpuscles and foreign particles 

 disseminated through a cubic metre or more of the 

 atmosphere 2. Such examinations soon convinced him 

 that the air of different localities varies very much 

 as to the nature of the particles which may be ob- 

 tained therefrom, but they also convinced him just as 

 much of the extreme rarity with which real spores or 

 ova are to be encountered. 



He says : — ^ I submit to the aeroscope the atmosphere 

 of towns and of marshes, that over the sea, and that in 

 mountain regions. In the first-named localities I find 

 it always surcharged with an infinite variety of organic 

 debris, and of that from other substances made use of 

 in our daily life. In that of the marshes and plains 

 one meets with an enormous quantity of fragments of 

 vegetable tissue. On the contrary, over the sea far from 

 shore, and on the mountains above the zone of human 

 habitation and of vegetable life, corpuscles of any kind 

 in the atmosphere become infinitely rare and infinitely 



^ Described in ' Compt. Rend.' 1. 1. p. 748. 



2 Dr. Maddox has also recently described a somewhat similar ' Appa- 

 ratus for collecting Atmospheric Particles,' which seems to be very- 

 portable and well adapted for the purpose. (See ' Monthly Microscopic 

 Journal,' June, 1870.) 



