G36 Profs. Cooke and Richardson on Absorption of 



Results of the Experiments. 

 The Table which follows contains the results of all the 

 measurements we have made. The data are set forth in 

 detail in order to show that formula (12) has been tested 

 under a great variety of conditions. This seems especially 

 important in view of the quite different results obtained by 

 Wehnelt and his pupils injheir experiments on lime-coated 

 wires. In the table, column I. gives the number of the 

 experiment. Column II. gives the mean deflexion D T of 

 the galvanometer G, in scale-divisions, caused by turning 

 the thermionic current on and off for 30-second intervals. 

 Column III. gives the mean galvanometer deflexion caused 

 by opening and closing the key K 3 for intervals of 30 seconds. 

 Column IV. gives the value of T, the thermionic current, in 

 microamperes. Column V. gives the value of z 1? the current 

 in the main circuit in amperes. Column VI. gives the re- 

 sistance R of the filament in ohms. Column VII. gives the 

 electromotive force of the battery B x in volts. Columns 



i 2 D T 2Rz 2 .v 

 VIII.— XI. give the values of the fraction ~ ^s- -^ — ] —~ c 



. . T D E ST(x+y) 



under different conditions. The value in column VIII. is 

 that obtained with the " filament shunted " and the main 

 current flowing in the direction from the filament to the 

 standard (F~>S) ; column IX. exhibits the corresponding- 

 quantity under like conditions, except that the main current 

 is reversed and flows from the standard to the filament 

 (S~>F). Columns X. and XI. are respectively the same as 

 VIII. and IX., except that the " filament shunted" arrange- 

 ment is replaced by the " standard shunted " arrangement. 

 If it were not for the effects which reverse when the current 

 ii is reversed the values in columns VIII. -XI. in any one 

 experiment should be identical and approximately equal to 

 <£. The differences in these numbers thus measure the mag- 

 nitude of these reversible effects, which are eliminated in 

 the final formula. It will be noticed that the divergence of 

 the numbers is much greater for the " standard shunted ' 

 than for the "filament shunted " arrangement. This is in 

 accordance with the theory of the measurements as developed 

 above, since the point at which i = i is nearer the centre of 

 the filament with the filament shunted arrangement. Column 



R* 

 XII. contains the value of <f> + 2 (6 — 6 ) calculated from 



(12). It will be noticed that both the "standard shunted" 

 and "filament shunted" arrangements give essentially 

 concordant values for this quantity. 



