216 
CHEMISTRY: W. D. HARKINS 
stars of the helium type to move. The black dots trace the path of the 
Milky Way. The paths sharply define a plane which is that of the 
stars used instead of the plane of the Milky Way, but in addition there 
are considerable tendencies of motion which carry the helium stars into 
other regions. In some cases this tendency seems to be the greater of 
the two. In the care of area 4 there is no tendency for a preference for 
motion in the Milky Way. 
To summarize the conclusions drawn from the investigation of the 
systematic motions of the helium stars, there appears to be a strong 
tendency for these stars to move in their own plane, which should there- 
fore be preserved, at least until the next step in the star's evolution. As 
a matter of fact the A-type stars, supposedly representing the next stage 
in evolution, exhibit a strong tendency to crowd toward this plane. But 
there are likewise strong tendencies for the stars of helium type to depart 
from the plane, so that the tendency for the stars to spread in every 
direction, so clearly manifest in advanced stages in the evolution of a 
star, has its birth in the helium stage of evolution. There is apparently 
nothing systematic in the motions directed away from the plane of the 
stars. 
THE ABUNDANCE OF THE ELEMENTS IN RELATION TO THE 
HYDROGEN-HELIUM STRUCTURE OF THE ATOMS 
By William D. Harkins 
KENT CHEMICAL LABORATORY. UNIVERSITY OF CHICAGO 
Received by the Academy, February 26, 1916 
According to the theory already presented in a number of papers^ 
the atoms of all the 91 elements of our ordinary system heavier than 
hydrogen are built up as intra-atomic (not chemical) compounds of 
hydrogen. The first of these 91 elements, heHum, is the second in the 
system, and therefore has the atomic number 2. It has an atomic 
weight of 4.00, and may be considered to be composed of 4 hydrogen 
atoms. The element of atomic number 3, lithium, has an atomic 
weight of about 7. Now it has been found that in general among the 
elements of low atomic weight, the elements of even atomic number, 
beginning with helium, seem to be built up from helium atoms, and 
therefore may be said to have the general formula ftHt', where the prime 
is added to indicate that these elements are intra-atomic, not chemical, 
compoimds. The odd numbered elements, beginning with lithium, seem in 
general to have the formula wHe'+Hs'. Thus the elements seem to fall 
into two series which may be called the even and the odd series, or the 
