THE MICROBES OF THE AIR 271 



The conclusion drawn from these investigations 

 are the following : 



(a) There are a larger number of microbes in the V 

 atmosphere during the summer than either the 

 spring or winter. They appear to reach a maximum 

 during the month of August. (&) The number of 

 microbes found in the atmosphere decreases, the 

 higher one ascends. Hence near the Lincoln Cathe- 

 dral there are fewer microbes in the atmosphere 

 (on any given day) than in the valley of the Witham. 

 The same remark also applies to the number of 

 microbes found in the atmosphere at the top of the 

 Trocadero Palace, Paris, where there are fewer 

 microbes than in a low-lying but crowded thorough- 

 fare like the Boulevard Saint-Germain, (c) There 

 are a" larger number of microbes in the atmosphere 

 of crowded centres than in less densely-populated 

 districts, (d) By gradually passing from a large 

 city towards the country the number of aerial 

 microbes decreases ; e.g., there are fewer microbes 

 in the atmosphere of the Forest of Ville d'Avray, 

 the Park of Versailles, and the village of St. Cloud, 

 than in the principal thoroughfares of Paris and 

 London. 



Dr. P. Miquel l (who is the greatest authority on 

 aerial microbes) has published elaborate tables con- 

 cerning the number of microbes in the air of certain 

 parts of Paris. During the year 1888, Miquel 

 obtained the following mean number of microbes in 

 the air (per cubic meter) at Montsouris, and in the 

 vicinity of the Hotel de Ville, Paris : 



1 Annuaire de T 'Obner vatoire de Montsouris, 1877-92. 



