77 



conditions that would forbid all existing vegetation. It is an 

 open question whether the plants referred to are survivors of an 

 earlier vegetation under different atmospheric conditions, or have 

 developed these remarkable habits under existing conditions. At 

 all events, they teach us that the atmospheric conditions which 

 would permit plant life are not necessarily those that obtain now. 



In reply to a question, W. A. Noyes spoke of the recent dem- 

 onstration by Cady and McFarland, of Kansas University, that 

 helium is a practically universal constituent of natural gas and 

 hence must be present in the atmosphere; also of the fact that 

 the presence of helium in natural gas indicates a wide distribu- 

 tion of radium, and has an important bearing, especially in con- 

 nection with the experiments of Strutt, upon the question of 

 the source of heat in the interior of the earth. 



In reply to another question, he also spoke of the two direc- 

 tions in which there is, at present, some prospect of rendering 

 the nitrogen of the air available for use as a fertilizer and in 

 other directions, namely, in the manufacture of calcium cyanam- 

 ide and in the manufacture of nitrates by oxidizing the nitrogen 

 of the air in an electric arc. 



C. E. M. Fischer: The niaintainance of a pure atmosphere 

 is an economic question of great importance, affecting as it does 

 the health and life of the community. 



Chemistr}' teaches us of what a pure atmosphere consists, and 

 also informs us of the various inanimate impurities which are 

 contained therein at various times and places. Biology tells us 

 of the various plant and animal spores with which the atmos- 

 phere is laden. 



Medical science owes it as e. duty to the community to make 

 use of the facts taught by chemistry and biology to bring about 



