THE AIR AND LIFE.* 



By Henry de Varigny, 



Every living thing' breathes, and to maintain life air is as essential 

 as water and food and a certain def^ree of heat. This sounds like an 

 altogether commonplace idea, and one over which there would be no 

 reason to linger were it not that modern science in its exact analysis of 

 phenomena has brought to light many curious facts which show how 

 varied are the relations between the living organism and its environ- 

 ment. 



Before we discuss these various relations, let us say a few words 

 about the air itself. It surrounds our globe on all sides to a height 

 not actually known, but as life probably can not be maintained beyond 

 10,000 or 15,000 meters, tlie air beyond that distance is of no interest 

 for our present purpose. It appears, ;uso, that there is no life in our 

 seas at a depth greater than S,000 or 10,000 meters, so that we may 

 say that all living things are contained in a stratum not more than 

 20,000 or L'5,000 kilometers thick. In this thin layer, wherein life attains 

 its maximum density at its central part, represented by the sea level, 

 all living organisms are contained. It is small when com])ared with 

 the dimensions of the earth and the immensities of celestial sjtace, but 

 it becomes all tlie more wonderful in view of the variety of the 

 forms evolved in it and the development attained by some of them. 



Each organism bears its portion of the weight of this atmosphere, 

 a person of average stature suppoiting several thousand kilograms. 

 The air contains aqueous vajior, holds in suspension different sorts of 

 dust, is stirred by numberless motions; and each of these qualities has 

 an effect upon life. 



Chemically considered, air is composed of various elements. It is 

 not a simple body, as was supposed up to the end of the last century, 

 but a mixture of gaseous bo<lies, susceptible of analysis and separa- 

 tion. It is a mixture and not a combination, for its elements unite 

 without electric or thermic phenomena, and it is a mixture in which 

 the relative pi()]>ortions of the component parts may be considered as 

 practically constant. 



Three of its elements preponderate either as to quantity or in physi- 



Translated from Heme des Deux Moiidcs, July, 1893; vol. cxviii, pp. 95-124. 



521 



