294 Mr Richardson, On the Negative Radiation 



At (absolute) = 1542° this gives A = 151 x 10 26 . The various 

 constants in the logarithmic equation come from the area of the 

 wire which was '394 sq. cm. and the value of the charge on an ion 

 which was taken to be 6 x 10~ 10 electrostatic units. The value of 

 m/R [m being the mass of, and R the gas constant for, one 

 corpuscle] was found to be = 1*204 x 10 -u . Putting this in the 

 expression for »n we find 1*3 x 10 -21 free negative ions in a cubic 

 centimetre of platinum at 1542° absolute. An independent value 

 of n has been obtained by Mr Patterson from experiments made 

 in the Cavendish Laboratory on the change of resistance of 

 platinum in a magnetic field. This when calculated by the 

 method given by Professor Thomson 1 yields % = l'37x 10 22 . The 

 agreement of the value found above with this is really very good 

 when one considers the numerous sources of error to which 

 the measurements are liable and that an error of 7 °/ in the 

 absolute temperature, among other things, would multiply the 

 value of n by ten. 



It was thought possible that some regular change of n with 

 the temperature might be observed if the values of n at different 

 temperatures were calculated. The deviations from the mean 

 however seem to be to a great extent purely irregular as is shown 

 by the following data, calculated from the first table : 



Absolute 

 Temperature 



1304 

 1331 

 1378 

 1419 

 1443 

 1463 

 1497 

 1516 

 1542 

 1571 

 1596 



The numbers in the second table yield similarly : 



•43 x 10 31 1467 



•58 x 10 21 1571 



•48 x 10 21 1692 



1-45 x 10 21 1722 



1-55 x 10 21 1763 



11 x 10 21 1806 



•98 x 10 21 1872 



1 J. J. Thomson, Rapports presentes au Congres International de Physique, in. 

 p. 138, Paris, 1900. 



No. of ions 



per c.c. 



of platinum 



1-2 



X 



10 21 



17 



X 



10 21 



1-8 



X 



10 21 



1-8 



X 



10 21 



1-95 



X 



10 21 



1-65 



X 



10 21 



2-0 



X 



10 21 



1-5 



X 



10 21 



13 



X 



10 21 



1-25 



X 



10 21 



1-2 



X 



10 21 



