Chemistry and Physics. 461 



A method of accounting for these results was suggested by 

 the writer in connection with his work with phosphorus nuclei 

 (Smithsonian Contributions, 1901, No. 1309). There may be 

 either generation or destruction of ions proportional to the num- 

 ber n present per cubic cm., in addition to the mutual destruction 

 on combination of opposite charges. In other words —dn/dt= 

 a + cn + bri 2 , where a is the number generated per second by the 

 radiation, en the number independently absorbed per second, and 

 bri* the decay per second by mutual destruction. If a is zero 

 (radiation removed) l/n — I/n =(l fii + b/c) (e c ( f— ( °) — 1) where 

 the nucleations n and n occur at t and t seconds. 



The fog chamber hardly admits of a sharp distinction between 

 b and c / but if the provisional values of the table be accepted, 

 since — (dn /dt) /n* = c/n + b, c will become rapidly more im- 

 portant as n falls below the order of 10 4 . All my data show this 

 conclusively. Again the c here obtained is of the same order as 

 the value found for phosphorus nuclei. Finally in case of equi- 

 librium in the pi'esence of radiation, dn ] dt = 0, the rate of pro- 

 duction becomes a = cn + bn*, where a measures the intensity of 

 the radiation. It no longer varies as n 2 . 



7. Electric Conductivity. — K. Badekee has determined this 

 conductivity for a number of oxides and sulphides of metals, and 

 also the thermoelectric force of these preparations. In general 

 the oxides and sulphides are of higher resistance than the metals. 

 This is shown in the following table : 



Cu 0-0000017 Cul 0-045 



Pt 0-000014 30 per cent H 2 S0 4 1-35 



Bi 0-00012 



CuS 0-000125 



PbO„ 0-00023 (?) 



CdO" 0-0012 



Ag„S (at 200°)... 0-0017 



Graphite 0*0028 



Cu 2 0-0028 



<XO 40- 



CuO ._ 400? 



The first three numbers give for comparison the resistance of Cu, 

 Pt, Bi.— Ann. der Physik, No. 4, 1907, pp. 749-766. J. t. 



8. Interference of Wireless Telegraph Waves. — F. Kiebitz 

 reaches the conclusion that it is possible to set many rectilinear 

 Hertz exciters in oscillation with determined phase differences, if 

 one connects them in a suitable manner with a system of stand- 

 ing waves. Moreover differences of direction were observed 

 which corresponded with phenomena expected from interferences. 

 —Ann. der Phys., No. 4, 1907, pp. 943-972. j. t. 



9. Pays of Positive Electricity. — Prof. J. J. Thomson has 

 studied the canal rays by means of phosphorescence. The end 

 of the canal ray tube was sprinkled with powdered willemite, 

 and the deflections of the phosphorescent spot under the com- 



