346 proceedings: Washington academy 



Society, W11.LIAM Gerry Morgan; Philosophical Society, W. J. Hum- 

 phreys. The National Geographic Society had nominated no Vice- 

 President. 



The newly-elected President, Dr. F. L. Ransome, then took the chair 

 and the retiring President, Dr. Lyman J. Briggs, delivered an address 

 entitled, The resistance of the air. This will be published in a later 

 number of the Journal. 



The 130th meeting of the Academy was held in the Assembly Hall of 

 the Cosmos Club, the evening of Thursday, January 30, 1919, the 

 occasion being an illustrated lecture by Major F. R. Moulton, U. S. A., 

 on The duration of the stars. Beginning with illustrations showing the 

 principal observatories of the United States and the apparatus by which 

 solar and stellar phenomena have been studied and photographed, 

 the lecturer showed photographs of the moon and of the sun, the one 

 an example of a completely dead world, the other an example of a world 

 which is giving off great quantities of energy and is very far from a 

 state of equilibrium. The source of the sun's energy was discussed 

 and shown to be a result neither of chemical reactions norof the energy 

 released by the contraction of an aggregate of particles. The latter 

 source would permit the sun a life of at most a few million years, whereas 

 geological and biological evidence demand periods of one hundred 

 million years or more. The source of the sun's energy and its probable 

 life cannot at present be estimated. 



After showing diagrams illustrating the relative size of the moon, 

 earth and sun, and the relative size of the orbits of the planets as com- 

 pared with the distances of the so-called fixed stars, the lecturer passed 

 to a consideration of the probable life of those stars. The problem of 

 the life of star clusters is one that can be dealt with mathematically, 

 and the lecturer calculated the probable period that must have elapsed 

 in order that a more or less heterogeneous collection of stars might, 

 by their mutual gravitation, be brought into the form now found in 

 many of the recognized clusters. In view of the immense distances 

 involved in the dimensions of these clusters, it follows that even a 

 single passage of one star from one side to another of such an aggregate 

 would take a million years; and the total time necessary to form the 

 aggregate as it is now seen must be of the order of several thousand 

 million years. 



An interesting digression at this point covered some of the lecturer's 

 work during the war, on the trajectories of projectiles and the best 

 form of projectiles to obtain maximum range. The problems involved 

 in this work were mathematical problems, in many ways similar to the 

 mathematical problems of the astronomer with which the speaker had 

 just been dealing, and he showed in a very practical way the wide 

 applicabiUty of mathematics as a working tool whether in the hands of 

 the scientist or the engineer. 



The lecturer finally considered the possible structure and location of 

 certain nebulae which have been made the subject of much study in 

 recent years. These may be distant galaxies equal in magnitude to the 



