46 



The Philippine Journal of Science 



191S 



was charged by means of an ebonite rod. The humidity, as 

 shown by a self-registering hygrometer, remained above 90 per 

 cent even at midday, and at night it was found necessary to heat 

 the ebonite rods in order to maintain the voltage. The number 

 of determinations is hardly sufficient to justify definite conclu- 

 sions, but the night determinations are all smaller than the 

 mean-day collection, and apparently the diurnal variation is the 

 inverse of that at Manila. Five daytime determinations made 

 at Manila with the apparatus as used on the mountain gave a 



I I ..4 ^.-=^ 



-^-k 



'o^^^t^ ^— 







V\c.. ',. Humidity, nctive deposit, and wind cmrves for February 4, 1914. 



mean value for the active deposit approximately one-half that 

 of Mount Maquiling. 



Ratio of the amount of radium active deposit to thorium active 

 deposit at Manila. — A wire was exposed as outlined above, and 

 the voltage was kept at 10,000 for ninety minutes. The dis- 

 charge was measured every three minutes after the introduction 

 of the cage into the ionizing chamber and the ionization curve 

 plotted. Thirteen closely agreeing determinations were made, 

 and the mean time required for the rate of discharge to fall to 

 one-half was found to be sixty-two minutes. According to the 

 determination of Harvey,'' this corresponds to less than 15 per 

 cent thorium active deposit. 



"Phys. Rev. (1912), 35, 9123. 



