INORGANIC IMPURITIES IN AIR. 247 



continued stationary. The following is M. 

 Que'telet's table of the mean electrical intensity 

 of the air, for the years from 1844 to 1848, both 

 inclusive, and the means of the same months in 

 the year 1849 : 



Other scientific observers have detected the 

 same peculiarities. We are unable to say, 

 however, that a deficiency in the electric in- 

 tensity of this atmosphere can be the cause of 

 this mysterious disease ; it must rather be looked 

 upon as an accomplishment of the phenomena 

 which produce cholera, and in all probability 

 partly concerned in their operation. 



In addition to the presence of organic par- 

 ticles, or, in other words, particles arising from 

 the decomposition of animal and vegetable 

 matters, it is certain that impurities of an inor- 

 ganic kind are often to be found in the air. In 

 large cities the rain which falls is always found 

 to contain coal ashes, soot, and sulphates and 

 chlorides of different kinds the latter probably 

 derived from the former thus proving the 

 large amount of impurity present in such at- 



