A Kinetic Model of the Electron Atom. 315 
be explained by assuming them to be due to certain motions and Cis- 
turbances which are seen in the experiment. The experiment lends itself 
to any or all of the theories as the fundamental assumptions may be 
changed to fit the particular theory in question. 
The classical method of performing the experiment is by floating 
magnetized needles by means of corks in water. I have found that 
small bicycle balls floated on mercury are much more convenient. (Pro- 
fessor Merritt used this method at Cornell University in 1900.) The 
mercury surface lends itself admirably for projection with reflected light. 
In projection it is well to focus not on the balls but on a plane a short 
distance above the balls or on the focal point of the concave mirror made 
by the depression caused by the balls. The position of the ball is then 
shown on the screen as a point of light. Fig. 5a is a photograph of 
three balls; the time of exposure is one-fifth of a second. Fig. 5b is a 
photograph of some thirty balls; the time of exposure is one-hundredth 
of a second. In this the balls are shown as points so fine that one can 
searcely see them in the photograph. 
Fig. 2 shows diagrammatically the arrangement of the apparatus for 
projection. A, C, and L are the arc, the condensing lenses, and the 
objective lense of a vertical projection lantern. M is a mirror with 
which the light is thrown down on the mercury in the tray, T. L’ isa 
lense with which an image of the balls floating on T is focused on the 
sereen, I. M’ is a mirror. N & S is an electro magnet which serves as 
the positive nucleus. 
In the classical Mayer experiment the balls are fixed. There is no 
motion. There is nothing to suggest how the atom may radiate. The 
