PART I. 



AN HISTORICAL ACCOUNT OF THE DEVELOPMENT OF 

 METHODS FOR DETERMINING OXYGEN. 



The interest in meteorology and aeronautics an interest ever increas- 

 ing and international in scope and the recent discoveries in the atmos- 

 phere of argon, helium, and their associated rarer gases, accentuate the 

 fact that the present information regarding the oxygen content of atmos- 

 pheric air, and, indeed, of the carbon-dioxide content, is far from satis- 

 factory. The known sources of oxygen are very limited in number, for 

 although it has been demonstrated that during certain periods of vege- 

 tative growth oxygen is liberated, the amount thus supplied to the atmos- 

 phere must of necessity be slight. On the other hand, the drafts upon 

 atmospheric oxygen are constantly increasing. Taking into considera- 

 tion those agencies that are directly or indirectly influenced by man, we 

 see that since both the population of the world and the combustion of 

 fuel are increasing enormously, this drain upon atmospheric oxygen must 

 to-day be very much greater than, for instance, during the Stone Age. If, 

 in addition, we consider the abstraction of oxygen by living organisms 

 other than man, the oxidation of organic matter and decay, and the oxida- 

 tion of iron, we find that all doubtless play an important role in decreasing 

 the percentage of oxygen in the air. With these various agencies at work 

 diminishing oxygen and producing carbon dioxide, it is to be expected 

 that variations in the density of population, in the number of factories, 

 in the distribution of vegetative tracts, and in the proportion of land and 

 sea, would lead to like variations in the composition of the air. The near- 

 est analogy to the atmosphere is sea-water, which, while vast in bulk, is 

 known to have differences in composition at different depths and with 

 different geographical distribution. 



If changes take place in the composition of the air, of what nature are 

 they? Are they measurable by our present methods of chemical analysis? 

 Do these variations bear any relation to the changing seasons, to growth 

 of vegetation, to rain, snow, and similar meteorological conditions, and to 

 geographical location? These are questions that have long been in the 

 minds of scientists, and, indeed, are to-day still debatable. 



Alterations in climatic conditions have been ascribed by Arrhenius 1 

 to relatively small changes in the carbon-dioxide content of the air. Thus 

 it seems that on meteorological grounds alone a study of the composition 



1 Arrhenius, Philosophical Magazine, 1896, pp. 237-276; also, Svenska Vetenskaps- 

 Akademiens Forhandlingar, 1901, 58, pp. 25-58. 



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