COLLEGE SCIENTIFIC SOCIETY MEETS.

Star (Christchurch), Issue 17906, 23 July 1926, Page 4

COLLEGE SCIENTIFIC SOCIETY MEETS.

.Commencing: with an historical survey of the field of investigation into the nature of X-rays, Mr It, M. N'imnio, M.So., gave an interesting lecture on -X-Rays and Crystal Structure” to the Canterbury University College Scientific Society last evening. Mr -i. Struthered by Rontgen, and ever since their disrovety their nature had been a subject of keen investigation. These rays were produced by the impact of cathode part a les, on a metal electrode. It was rays and the CanalstrahTn or positive rays, had their unaffected by rise to the theory that X-rays consisted of cathode parts, or negative electrons which had attached to them a positive charge, and hence were neutral. Such particles would in their flight be uripassed out through the walls of the X-iav tube. A mathema t i«-al analysis of the state, of the electric magnetic field when a moving electron was stopped Suddenly was undertaken by Schuster, Stokes, J. J. Thomson and others, arid Ht was shown that the stoppage of such an electron would be accompanied by an electromagnetic pulse in the ether, in fa*-t. a radiation very similar in nature to light waves. Various observed phenomena, notably the polarisation of the rays, supported this theory', bur there was one vital objection. AIT light waves were bent when other. One was 1 familiar with the apparent bending of a stick when it was Placed in water. This was due i„ the bending of the rays of light when they -passed from water t«. air. No medium, however, could be found which would produce a bending in the X-rays. No solution could l*e found to the question of the nature of X-rays until Rane conceived the idea of using the ordered arrangement of atoms in a crystal as the rulings of the grating. lie showed that if a beam of X-rays were passed through a crystal the difTi a. I ion ea used beams 6f X-rays in certain definite directions. y. ml a photographic plate a series of smaller spots where the diffracted rays met the plate. The experiment was carried out by Friedrich and Knipping in with great success. R> means of diagrams, Mr Ximmo explained how the simple space lattice the various methods of analysis of crystal structure. At the conclusion of the lecture Mr