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THE POPULAR SCIENCE MONTHLY. 



and estimating the spores deposited by those volumes, and from this 

 deducing the number of spores contained in a cubic metre of air. 

 Repeating these measurements every day and every hour for several 

 years, and taking care to notice all the anterior or concomitant meteor- 



M D 



Fig. 2. Pollen and Dust in the Atmosphere. 



ological conditions, he succeeded in defining the influence of the sea- 

 sons, and of temperature, dryness, and moisture in the progress of the 

 phenomenon. 



This method, applied at the Montsouris Observatory, shows that the 

 number of mold-spores is weak in January and February, diminishes 

 in March, and rises in April ; the increase is very sensible in May, and 

 the maximum is reached in June. The number then diminishes slowly 

 till October, considerably in November, and reaches a minimum in 

 December. 



It may be said, generally, for the locality where the experiments 

 were made, that a cubic metre of air contains on the average seven 

 thousand mold-spores in December, January, and February ; twelve 

 thousand in May ; thirty-five thousand in June ; twenty-three thou- 

 sand in August ; fourteen thousand in October, and eight thousand in 

 November. If, instead of considering the means of several years, we 



