AIR AND LIFE. 161 



the assertion. While we know that ozone is nothing more than oxygen 

 in an altered and allotropic condition, we are quite in the dark as to the 

 methods by which this alteration is effected. We know that the ratio 

 of ozone is very variable ; that it is more abundant in May than in any 

 other month; more abundant in the morning, from October to June, 

 and in the evening - , in July, August, and September, so that, upon the 

 whole, it seems to follow fair weather and heat; but this hardly helps 

 to solve the question, and much remains to be discovered. 



Concerning ammonia, our information extends somewhat further than 

 in the case of ozone. Ammonia is constantly present in the atmosphere. 

 In 1S57 Boussingaulf and, later, Schloesing, did good work in reference 

 to this subject. They have shown that ammonia generally exists in 

 combination with carbonic or nitric acid; only a small proportion is free. 

 Its origin is easily ascertained, for ammonia is one of the by-products 

 of organic rmtrefaction. Considering the amount of putrefaction which 

 must take place on our planet, it is clear that this source is a fruitful one; 

 and it must be added also that ammonia could not exist in an atmos- 

 phere where life was absent, nor in one where putrefaction was impos- 

 sible, nor in an entirely aseptic atmosphere, the organisms themselves 

 being aseptic. Although ammonia is a constant component, it is a very 

 small one; air does not contain more than a few millionths of it; but 

 water of atmospheric origin, rain, vapor, fog, etc., holds a larger propor- 

 tion. M. Schloesing has devised ingenious apparatus and methods for 

 ascertaining the proportions of ammonia in air and in rain water, as the 

 matter is one of importance, particularly to agriculture, in view of the 

 interchange of ammonia that occurs between air, rain, and ground water. 

 One of the results has been to show that each hectare in France (some- 

 thing over 2 acres) receives yearly through rainfall, or from the atmos- 

 phere, 9.801 kilograms of nitrogen under the form of ammonia. This 

 will be again referred to further on, when we come to consider the uses 

 of this compound and its role in nature. 



Other nitrogen compounds are also present in air — nitrous and nitric 

 acids, for instance, both in very small quantities. It may be that they 

 are formed under the influence of atmospheric electricity, as some experi- 

 ments by Cavendish seem to show, and as indicated by some observa- 

 tions of Liebig, who detected nitrate of ammonia in the rain that falls 

 during thunderstorms. It may be ailso, as Schoenbein suggests, that 

 nitrous acid is formed by the action of nitrogen on water during the 

 different oxidizations or combustions which goon rapidly in our works, 

 factories, and so forth, and slowly in the field of nature. Nitric nitrogen 

 is more abundant in and during winter, and it is more especially in rain 

 water that its proportions have been ascertained. Generally some 0.73 

 milligram are present in each liter of rain water, and in France each 

 hectare receives about 3.9S6 kilograms of this nitrogen through the 

 rainfall. Added to the nitr >geu received under form of ammonia, this 

 gives us a total of 13.787 kilograms of nitrogen received by the soil. 

 SM 95 11 



