SUMMARY OF THE EXPERIMENTS. 567 



1138. SUMMARY OF THE EXPERIMENTS. Apart from the method 

 of Weber and Kohlrausch, in which the value of a is taken solely 

 from the numbers given by the experiment itself, the other methods 

 bring in the numerical value of a resistance, which has often been 

 determined by the British Association. If we assume (1128) that 

 the most probable value of the ohm is represented by 106*25 cm - 

 of mercury, the unit (B.A.U.) is equal to 0-98664. By correcting 

 the results for the error made in estimating the resistances, we find 

 as means of the numbers obtained by various experimenters : 



Value of a 



Date and Observer. > -^ - xx - -^ 



Found. Corrected. 



1856. Weber and Kohlrausch ... 31*07. io 9 3i*o7.io 9 



1869. W. Thomson and King... 28*46.io 9 28-08.10 



1872. Dugald McKichan 29-35. io 9 28*96. io 9 



1880. Shida 29*95. io 9 2 9'55- IC)9 



1879. Ayrton and Perry 29*8o.io 9 29*6o.io 9 



l88 3- J- J- Thomson 29'2o.io 9 29*2o.io 9 



1884. Klemencic 3o*i9.io 9 30*19. io 9 



Mean 29*52. io 9 



The most recent researches have given for the velocity of light : 



1862. Foucault 29*80. io 9 



1874. Cornu 30*04.10 



1879. Michelson 29*98. io 9 



It will be seen that, in all probability, or at any rate with an error 

 which is less than one per cent, the velocity of light in a vacuum, 

 and the ratio of the electromagnetic and electrostatic units of elec- 

 tricity, are represented by the same number. 



