Show HIGH SPEED collisions OF NUCLEI OF ATOMS photographed remarkable photographs poto graphs of high speed collisions of the nuclei of atoms obtained by the use of a moving picture machine were shown by dr william draper harkins of chicago university in a series of lectures march 7 8 and 9 at carnegie institute of technology pittsburgh A new discovery by use of the photos was that the helium nucleus used as a projectile rebounds in a backward direction while the nucleus of the nitrogen atom which is hit is projected forward both at speeds of several thousand miles per second dr harkins who discussed the general subject of isotopes and the building and disintegration of atoms spoke before representative audiences of pittsburgh scientists at each lecture he traced the development of the atomic thory from its purely speculative beginning in the minds of the ancient philosophers to its present status as an experimentally demonstrated fact evidence was shown that each individual atom is a very complex body which may be likened to a minute solar system whose constituent parts may attain a velocity of many thousand miles per second in describing the discovery of radioactivity and of radium he showed how these discoveries have enabled scientists to draw an accurate picture of the atom with its central sine or positively charged nucleus and its attendant planets or charges of negative electricity called electrons the fact that many substances such as lead and chlorine which were formerly considered elementary and now known to 0 be mixtures of substances which resemble one another closely were shown to have an important bearing on the subject of the constitution of the atom the separation of these almost identical substances called isotopes was described dr harkins further developed the theory that the complex atoms are built largely from atoms of helium which may be regarded as the atomic building blocks capable of being assembled into various structures |