ABSTRACT OF PROCEEDINGS. 
XV. 
water must be regarded as unsatisfactory for irrigation, unless the total 
soluble solids were very low. Limiting values used in assessing water 
suitability for stock were also discussed and the need to consider such 
factors as the access of stock to green feed, &c., was stressed. 
Abstract of Proceedings, 29th October, 1945. 
The Ordinary Monthly Meeting of the Society was held in the 
Geology Department of the University on Monday, 29th October, at 
8 p.m., with the President (Prof. H. J. Wilkinson) in the chair. About 
forty-five members and friends were present. The minutes of 
the previous meeting were read and confirmed. Mr. 0. T. Fenwick, 
Mr. R. Riek and Dr. S. Julius were elected to Ordinary Membership. 
The meeting celebrated both the jubilee of the discovery of X-rays 
and the centenary of the birth of W. C. Rontgen. Dr. H. C. Webster, 
the first speaker, said that the discovery of X-rays arose from experi- 
ments with a cathode-ray tube and a fluorescent screen of barium 
platinocyanide. When the screen was placed near the cathode-ray tube 
(previously covered with black paper) it glowed when the current 
passed through the tube. The discovery of the penetration of tissues 
and of the differential absorption of bone and tissue followed almost 
immediately. Since Rontgen ’s days immense strides have been made 
in producing X-rays of greater intensity and penetrative power and 
generators of up to 100 million volts have now been constructed. 
Exact controllability of output is also a feature of modern equipment. 
The remainder of the paper was devoted to a review of the non-medical 
uses of X-rays. The discovery of X-ray diffraction gave rise to two 
fields of investigation — firstly, of the wavelengths of X-rays, and, 
secondly, of the structure of crystals. The first has aided in the 
discovery of new elements and in the identification of impurities. It 
has been most fruitful in providing information regarding the structure 
of certain parts of atoms. The second has provided information 
concerning heat treatment of metals, strains in castings, the structure 
of wool and other animal and vegetable fibres, &c. The radiography 
of materials has also had widespread uses, such as differentiation 
between lead and soda glass, detection of foreign bodies in packaged 
goods, examination of defective wood, fruit, &c., detection of faked 
pictures, and many others. The paper concluded with a warning against 
the dangers of use of X-rays for frivolous purposes. 
Dr. Yal McDowall stated that in 1895 W. C. Rontgen discovered the 
rays which he called X-rays, on account of their so far unknown charac- 
teristics. The first improvement to be made in the production of 
X-rays, the placing of the target or anode in the vacuum tube, was 
made by Herbert Jackson. In 1896 Dr. C. F. Marks, Brisbane, 
imported the first X-ray apparatus in Australia. Advances in radio- 
graphy can be divided into four periods: — (1) The induction coil and 
gas tube period from 1896 to 1914. (2) The interrupterless transformer 
and hot cathode tube period, which overlapped the induction coil 
period, but which came into general use about 1918. (3) The period 
of valve rectification and mechanical interruptors was replaced by 
