686 THE UNIVERSE. 



mountains, the nearer we approach populous cities, the more 

 does the air become loaded with invisible particles. The 

 catalogue of these is in reality only the summary of all that 

 man makes use of for his wants or pleasures. We find 

 atoms of food, of our clothes, of our furniture, and of our 

 dwellings ; everything, in short, is represented there. 



The flour of wheat, which constitutes the basis of our 

 food, and is used everywhere, is disseminated everywhere 

 by the air. By means of this fluid it penetrates into the 

 most secret recesses of our dwellings and monuments. I 

 have discovered it in the most inaccessible nooks of our old 

 Gothic churches, mixed with dust blackened by the antiq- 

 uity of six or eight centuries ; I also found some in the 

 palaces and crypts in the Thebais, where it perhaps dated 

 from the epoch of the Pharaohs ! 



In our cities it is one of the most abundant corpuscules in 

 the air; the falling snow and the wheeling insect take up an 

 enormous amount as they traverse it. I have counted as 

 many as forty or fifty grains on the wings of certain flies. 

 It also attaches itself to the surface of the body of man and 

 large animals. 



We also discover in the air the skeletons of different in- 

 fusoria, and, what is still more extraordinary, we even find 

 there animalcules perfectly alive. We also frequently meet 

 with the debris of insects, filaments of wool, silk, or cotton, 

 tinged with the most various colors ; likewise abundant 

 refuse of the soil, and even particles of smoke expelled from 

 our manufactories and household fires. Everything is found 

 here, and with a little practice can be readily recognized ; 

 and the only things we do not encounter, or what is at any 



