■242 BEARINGS OF METEOROLOGY AON GRICULTURE, ETC. 



of 1,363 grammes of ammonia was poured in rain on each square meter of 

 the park of Montsouris, or more than thirteen kilogrammes per hectare. 

 The quantity of other gaseous constituents carried down by the rain, and 

 the irreguhir impurities it washes out of the atmosphere, are also recorded. 

 The mention of impurities in the air naturally suggests the valuable ser- 

 vices which meteorological research appears destined to render to iDublic 

 health. If air be drawn tor some days through a tube containing carded 

 cotton, the cotton will be found to have turned gray, through the powdery 

 matters it has intercepted. Now these powders are well worthy of being 

 studied. Their nature is very varied ; they contain such material matters 

 as carbonate of lime, carbon, iron, also the debris of tires, spores of crypto- 

 gamie plants, pollen, grains of starch, etc., and excessively minute grains 

 which are probably the germs ef living creatures. For more than a year 

 these powders of the air have been subjected, at Montsouris, to daily micro- 

 scopic analogy, and, in relation to the germ-theory of disease, which now 

 engages so much thought, the results can hardly fail to prove of great value. 

 It will be seen whether there is really a strict correlation between endemic 

 or epidemic disease, and the frequency, local or general, of germs borne in 

 the atmosphere. Perhaps it will be possible by and by to say what kind 

 of germs produce particular kinds of disease, and to take protective meas- 

 ures accordingly. Indeed, not a little has been accomplished in this direc- 

 tion already, through the researches of Beale, Sanderson, Klein and others. 

 One of the means employed at Montsouris for collecting the organism& 

 of the air consists in directing a slow current of air, produced by a small 

 bellows, upon a drop of glj^cerine. In this way are especially caught the 

 spores, pollens, particles of meteoric iron, starch grains, and debris of all 

 kinds carried about by the wind. But the fine germs, which are of more 

 importance, are apt to escape notice among the larger corpuscles; and, be- 

 sides, in glycerine they lose the mobility which they show in water. So 

 they are better observed in drops of water resulting from the condensation 

 of atmospheric vapor, in night dew, in the first drops of rain, or in the dew 

 which forms on the outside of a vessel with a freezing mixture in it ; or, 

 again, after washing the air with water from a spray-producing apparatus. 

 Moving organisms, as has been stated, are often met with in such water^ 

 and their rotatory or irregular movements leave no doubt as to the real na- 

 ture of these minute corpuscles; they are vibriones and bacteria. Some- 

 times, chiefly in February and March, minute colorless corpuscles, with a 

 circular motion, are observed, which are thought to be mostly zoospores. 

 Germs of infusoria are also frequently present. The spores of cryptogami 

 become more abundant toward May. 



Last year the municipal authorities of Paris, having decided that m^ete- 

 orological researches with reference to public health should be carried on in 

 various quarters of the city, charged Montsouris to make arrangements for 

 this purpose, and promised an annual grant of 12,000 francs. The new 

 system, inaugurated this year, comprises at present twenty-one stations dis- 



