PROFESSOR JACK

Southland Times, Issue 18853, 19 June 1920, Page 5

PROFESSOR JACK

■ ATOMS AND THEIR RADIATIONS." Every iivailabl seat in the Victoria Hal! was occupied last evening when Professor ■Jack, or Otago University, delivered an illustrated lecture on “Atoms and Tlierr Radiations.” The lectur, which was given under I he auspices of the Invercargill branch of the W.E.A., was of more than ordinary interest, and unlike many lectures on scientific subjects, was almost entirely free from the technicalities which are frequently not understood by the larger portion of the audience. Professor Jack treated his subject as simply as possible, and by the aid of lantern slides and other illustrations, was able to convey to his audience (he meaning of (he various phases of the subject with which he dealt.

Considering first the nature of the atom, the lecturer slated that it might be said that matter consisted of a small number of substances; and that these substances consisted of molecules. The size of a molecule could be illustrated by the size of a water drop magnified to the size of the earth. The molecule would then be the size of a football. These molecules consisted of smaller portions called atoms. The atom consisted of electrons moving in rings around a nucleus consisting of hydrogen and helium. In this connection it was pointcri out that Professor Rutherford had within the last year produced hydrogen from nitrogen. Referring to the disturbance of the atom, he stated that Alpha, Beta and Gumma rays were sent out from the nucleus. 'lhe atom was a great store of energy and some day the key to unlock that store might be found. In describing Ihe disturbances due to electrons, Professor Jack gave several interesting illustrations by means of vacuum tubes, Crookes’ spinthariscope and luminous powders. In regard to the vibrations which produced visible light, he si ated that these could be separated out, thus forming a spectrum. There were three classes of spectra. One was known as the continuous spectrum which was given out by incandescent solids and liquids could be seen by direct vision through the spectroscope. The second class was the bright line spectra which were given out by incandescent gases. These bright lines appeared in definite positions for definite substances, thus enabling scientists to identify a very .small amount of substance and to determine the constituents in nebula, comets, solar prominences and the corona. The third class was known as the absorption spectrum and was produced when a light from it hot solid passed through a cooler gas and could be illustrated by considering that when a particular note was sung into a piano the string which would give out that note absorbed the sound.

Professor Jack also spoke interestingly on the effect of magnetism on light, and also dealt with polarised light, which he stated was used practically in the design of machinery and in the examination of sugar solution. Professor Jack was frequently applauded during his ' address and was accorded a hearty vote of thanks.