PROCEEDINGS OF THE SECTIONS. 
Section A. 
ASTRONOMY, PHYSICS, MATHEMATICS, AND 
MECHANICS. 
President of the Section: R. Threlfall, M.A., Professor of Physics, 
University of Sydney. 
1—THE ELASTIC PROPERTIES OF QUARTZ 
THREADS. 
By R. Turetratt, M.A., Professor of Physics, University of 
Sydney. 
| Abstract. | 
THE research of which the following is an abstract was carried 
out in the Physical Laboratory of the University of Sydney, 
with the assistance of Messrs. J. F. Adair and J. A. Pollock. 
The undoubted superiority of quartz fibres for purposes of 
suspension led the author to undertake the present investigation, 
in order to supply the requisite data to instrument makers, and 
to physicists engaged on the designing of instruments. The 
investigation of most of the elastic properties of quartz threads 
depends on the accurate estimation of the thickness of the threads 
used. The microscopic methods of measuring the quantity were 
made the subjects of special enquiry, and it is shown that in the 
measurement of tibres of the order of -01 cm. diameter con- 
stant errors may be practically avoided, and accidental errors 
reduced to 3 or 4 per cent. per measurement. The greater 
portion of the uncertainty of a single observation can be eliminated 
by multiplying the observations. A new method of drawing 
threads suitable for the production of short, thick fibres was 
devised. The following points were investigated :— 
1. The breaking strength of fibres of various thicknesses, 
investigated in two ways. 
2. The simple rigidity of quartz fibres. 
3. The temperature co-efficient of the simple rigidity. 
4, The temperature co-efficient of the total torsional rigidity 
of cylindrical fibres (the datum to be used in instru- 
