294 
Mr Richardson, On the Negative Radiation 
At 0 (absolute) = 1542° this gives A = 1*51 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 n = P37 x 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 °/ 0 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 : 
No. of ions per c.c. 
Absolute 
of platinum 
Temperature 
1*2 x 10 21 
1304 
1*7 x 10 21 
1331 
1-8 x 10 21 
1378 
1*8 x 10 21 
1419 
1*95 x 10 21 
1443 
1*65 x 10 21 
1463 
2*0 x 10 21 
1497 
1*5 x 10 21 
1516 
P3 x 10 21 
1542 
1*25 x 10 21 
1571 
1*2 x 10 21 
1596 
numbers in the second table yield similarly 
*43 x 10 21 
1467 
*58 x 10 21 
1571 
*48 x 10 21 
1692 
1*45 x 10 21 
1722 
1*55 x 10 21 
1763 
IT 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. 
