58 
PHYSICS: TOLMAN AND STEWART 
1 For references, see Richards and Barry, /. Amer. Chem. Soc, Easton, Pa., 37, 1915' 
(993-1020). 
2 Washington, D. C, Bull. Bur. Stand., 11, 1914, (243). 
3 Richards and Barry, Loc. cit. 
* Richards and Osgood, /. Amer. Chem. Soc, Easton, Pa., 37, 1915, (1718-1720). 
6 Stohmann, /. prak. Chem., Leipzig, 39, 1889, (514). 
6 Benedict and Fletcher, /. Amer. Chem. Soc, 29, 1907, (739-757). 
' Richards, Frevert, and Henderson, Boston, Mass., Proc Amer. Acad., Arts. Sci., 42, 
1907, (584). 
'Auwers, Roth, smdEisenlohr, Liebig's Ann. Chem., Leipzig, 385, 1911, (102-116). 
9 Richards and Barry, /. Amer. Chem. Soc, Easton, Pa., 36, 1915, (997). 
" Roth and Auwers, Liebig's Ann. Chem., Leipzig, 407, 1914, (154, 158). 
"For example, 2-4 Dimethyl hexane, boiling point 110°, L. Clarke, /. Amer. Chem. 
Soc, Easton, Pa., 30, 1908, (1148). Octanes have higher specific heats of combustion than 
toluene. (Richards and Jesse, Ibid., 32, 1910, (292). 
THE MASS OF THE ELECTRIC CARRIER IN COPPER. SILVER AND 
ALUMINIUM 
By Richard C. Tolman and T. Dale Stewart 
Communicated by R. A. Millikan, November 28, 1 91 6 
In a previous article [Physic. Rev., 8, 97 (1916), these Proceed- 
ings 2, 189 (1916)] we have described some experiments in which a coil 
of copper wire was rotated about its axis at a high speed and then 
suddenly brought to rest, the ends of the coil being connected with a 
sensitive ballistic galvanometer which permitted a measurement of 
the pulse of current which was produced at the instant of stopping by 
the tendency of the electrons to continue in motion. 
We have continued these experiments making use of three new wind- 
ings of copper wire, and using two different windings each of silver 
and aluminium wire. These further experiments were made, not 
only because it seems desirable to subject so new a phenomenon to a 
more rigid test, but because it is also desirable to see if the mass of the 
carrier of electricity is the same in all different metals and how much 
it differs, if at all, from the mass of the electron in free space. . 
We now have a record of the results of 624 individual runs made on 
a number of different coils, using three kinds of wire, two different sizes, 
and two different kinds of insulating binder to hold the coils in place. 
The runs were made with various total resistances in the circuit, with 
various lengths of wire, and at various velocities, rotating sometimes 
in one direction and sometimes in the other. Not only was the pulse 
of electricity every time in the direction which would be predicted on 
the basis of a mobile negative electron as the carrier of electricity, 
