30 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
of the elements have informed us that atoms must be .complex. 
But only after the discovery of X-rays and radioactivity did 
detailed truth begin to appear. Today we find ourselves at a 
time when the most conservative will admit the necessity for an 
atom consisting of a very small nucleus, less than one ten- 
thousandth the atomic radius, surrounded by electrons, pre- 
sumably in orbital motion. The conception of the atom as a 
solid elastic sphere has now completely disappeared, save in so 
far as it is useful in theories yet in a crude and approximate 
state, .such as the kinetic theory of gases. In fact there is con- 
siderable evidence that the atom is not symmetrical in shape. 
The collision .between atoms does not now find its analogy in the 
clash of billiard balls, but in the orbital hyperbolic motions in the 
solar system. Collision involves not contact but an electrical re- 
pulsion occurring upon the close approach of the positively 
charged nuclei. Cohesion is occasioned by an electrical . attrac- 
tion. Time was when we sought a mechanical explanation of 
electrical phenomena. Now we attempt to explain all in terms 
of electricity, in terms of that which once was thought to be a 
superficial effect obtained by rubbing two bodies together. 
Surely, we have come upon a day when the scientific men meet 
eye to eye with the philosophers, the former seeing a new vision 
and the latter adopting the new revelations in matter with a zeal 
which portends a new era in philosophy. 
One of the most notable recent achievements in our own coun- 
try is that which must be credited to him who was to give our 
annual address. Professor Millikan has succeeded in demon- 
strating and measuring with a satisfactory degree of accuracy 
the unit of electricity. Numerous physicists contributed in a 
more or less direct way to the final successful measurement, and 
among these should here be mentioned our own Professor Bege- 
man. 
Evidence of the inadequacy of any theory of light requiring 
a continuous wave front, is accumulating. The quantum con- 
ception of light is receiving each year additional confirmation. 
The recent notable contribution in this field is the establishment 
of this quantum relationship in photo-electric effect and in the 
emission of characteristic X-rays. It would seem that, while 
the intensity of radiation does diminish with distance from a 
point source in accord with the inverse square law, yet the 
