398 abstracts: physics 



that the 1913 results from 8 magnetic observatories indicate on the 

 average an increase of about 0.002 of a per cent in G, and a decrease of 

 about 1 per cent in the magnetic diurnal range for a decrease of 1 

 per cent in the solar constant. 



It is shown further that the eclipse magnetic effects are of the same 

 sign, and of the same order of magnitude as the magnetic effects which 

 are, apparently, to be associated with about a 10 per cent decrease in 

 the value of the solar constant. 



It is found that on consecutive quiet days the magnetic constant is, 

 on the average, larger on the second day than on the first by an amount 

 equal to that which would be caused by the average daily change in the 

 solar constant. If the quiet day magnetic effect were to persist through- 

 out the year, it would cause a secular variation fully 10 times that gen- 

 erally observed. However, the quiet days are in the minority, and on 

 the unquiet days the effect is in a direction opposite to that for the 

 quiet days. Since there is not a complete compensation between the 

 two opposing effects when integrated throughout a period of a year, 

 part of the observed secular magnetic change should be of a type related 

 to the annual change in solar constant. W. F. G. S. 



PHYSICS. — On the ionization of the upper atmosphere. W. F. G. 

 Swann. Terr. Mag., 21: 1-8. 1916. 



If the sun is taken as a black body, and if in accordance with the 

 experiments of Hughes, ionization does not set in below wave length 

 135 nn, it appears that only about 1.6 X 10 -5 of the total solar radiant 

 energy is available for atmospheric ionization. 



The results are applied to an example cited* by Schuster in connec- 

 tion with his theory of the diurnal variations of terrestrial magnetism. 

 Schuster concludes that if the upper atmosphere is treated as a shell 

 300 kilometers thick, at a pressure 1 dyne per square centimeter, a con- 

 ductivity of 10 -13 e. m. u. would have to exist in it in order to account 

 for the necessary magnetic effects. The author finds that only about 

 10~ 3 of this amount can be accounted for in such a shell, by the ultra- 

 violet radiation, and even if the whole of the sun's energy could be 

 absorbed in producing ionization, the conductivity accounted for would 

 yet be far too small. 



The above conclusion is not intended as a criticism of Schuster's 

 theory, however, since the ultra-violet light is not the only source of 

 ionization in the upper atmosphere. Further, it is shown that if the 

 calculation is not limited to a shell, but if account is taken of the infi- 



