proceedings: biological society 271 



which a corpuscle travels from its point of origin, the corpuscular 

 current density will be 



i — qeh 



where e is the electric charge. 



If account be taken of the fact that the radiation passing through 

 1 sq. cm. comes from all directions lying within a hemisphere, the 

 result is to introduce a factor of \, so that 



i = h qeh 



The average value of the air-earth current density as obtained 

 from several stations is 6.7 X 10~ 7 E.S.U., so that if q be taken as 

 3, which is about equal to the number of pairs of ions produced per 

 cubic centimeter per second in a closed vessel, as a result of the part 

 ' of the penetrating radiation in question, the value of h necessary to 

 account for the measured current-density is 9 meters. This value is 

 quite within the range of posibility, since Eve has observed /3 rays at 

 a distance of 7 meters from the source. 



A few minor difficulties present themselves. Thus, for example, 

 near the surface of the Earth a considerable portion of the whole 

 penetrating radiation comes from the soil, and is directed upwards, 

 but this difficulty disappears when it is remembered that the average 

 "hardness" of this radiation is very much less than that of the radia- 

 tion which reaches the Earth from the outer layers of the atmosphere. 

 Again, it might appear that the corpuscles set free by the penetrating 

 radiation should, on account of their great energy, produce in the 

 atmosphere many more ions per second than are actually found to 

 be produced. This difficulty and others of allied nature become 

 greatly reduced in magnitude, however, when considered in the light 

 of our present knowledge of the action of very swift (3 rays when pas- 

 sing through a gas. 



Discussion. Mr. Bauer spoke of the possibility of some of the 

 penetrating radiation being of solar origin. 



Donald H. Sweet, Secretary. 



THE BIOLOGICAL SOCIETY OF WASHINGTON 



The 568th regular meeting of the Society was held in the Assembly 

 Hall of the Cosmos Club, Saturday, March 24, 1917; called to order at 

 8 p.m. by President Hay; 31 persons in attendance. 



Under the heading of book notices Dr. L. 0. Howard said he had 

 carefully examined the work on beetles presented to him at the 567th 

 meeting of the society by Dr. H. M. Smith, and found that it was a 

 hand made copy of all the descriptions of the North American beetles 

 contained in a large French monograph dealing with that group of 

 insects. 



The regular program consisted of three communications: 



