71 



SYMPOSIUM OIsT THE 

 ATMOSPHERE 



Opening Address by T. C. Chamberlin. 



In opening the symposium Mr. Chamberlin dwelt chiefly on 

 recent deductions relative to the distribution of atmospheric 

 molecules outside of the recognized atmosphere and occupying 

 in an attenuated way the remainder of the sphere of control of 

 the earth. The basis of these deductions lies, in the main, in 

 the accepted principles of the kinetic theory of gases, but the 

 application of these principles is modified by sources of molecu- 

 lar agitation springing from radio-activity and electric disso- 

 ciation. In the lower horizons of the familiar collisional atmos- 

 phere the molecules are held to move to and fro encountering 

 one another some billions of times per second. They therefore 

 pursue essentially straight paths at equal rates between en- 

 counters, because the interval is too short to permit gravity to 

 curve their paths. But as we ascend to the upper regions of 

 the collisional atmosphere the distances between encounters in- 

 crease until at length the free paths are sufficiently long to be 

 curved by gravity. At still greater heights curved paths come to 

 dominate, and the spacing becomes so open that occasional mole- 

 cules, rebounding outwardly from collisions, do not encounter 

 any other molecules in their paths. In these cases the mole- 

 cules go outward until the attraction of the earth stays their 

 progress and starts a return movement toward the collisional 

 atmosphere, which increases' in velocity until an encounter takes 



