74 PROCEEDINGS. 



The Chairman announced that an advanced copy of the new 

 monthly issue of the Society's Journal for the present year lay 

 upon the table for the inspection of the members, and would be 

 ready for distribution in the course of a few days. 



A letter was read from the proprietors, inviting the members 

 to visit the Aquarium at Manly. 



In the absence of the author, the Hon. Secretary (Mr. F. B. 

 Kyngdon) read a paper by Mr. H. G. McKinney, M.E., M.I.C.E., 

 entitled " Notes on the Experience of other Countries in the 

 Administration of their Water Supply." 



The thanks of the Society were accorded to Mr. McKinney for 

 his valuable paper, and it was resolved that the discussion upon 

 the same be postponed until the following meeting. 



Exhibit. 



Professor Warren exhibited and described the following 

 apparatus : — 



"An apparatus for measuring minute strains occurring within 

 the limits of Elasticity, devised by Mr. P. Y. Appleby and Prof. 

 Kennedy, also an Autographic Stress-strain apparatus, devised 

 by Mr. A. G. Ashcrof t and Professor Kennedy " ; described and 

 exhibited by Professor Warren. 



During the last few years a considerable amount of work has 

 been done with regard to the effect of stresses in producing strains 

 in materials, under a great variety of conditions. The materials 

 which have been more thoroughly investigated in this direction 

 are steel and iron. Several ingenious contrivances have been 

 devised by various experimenters for measuring such small strains 

 as xoloo part of an inch in a steel or iron test piece. The extension 

 produced by stresses within the limit of elasticity is a measure of 

 the modulus of elasticity. 



According to Prof. Unwin an error of T cro o o part of an inch in 

 the extension of a steel bar 10 inches long with a load varying 

 from to 10 tons, would mean an error of 2 per cent, in the 

 modulus of elasticity, and in trying to determine the extension 

 from ton to ton, an error of to "oo o part of an inch would make an 

 error of 20 per cent, in the extension per ton. Hence the 

 importance of using instruments capable of measuring small 

 elongations accurately in all experiments on modulus of elasticity. 

 The little instrument which I have the pleasure of shewing you, 

 has been in use for the last two years at the University of Sydney 

 in determining the modulus of elasticity of a great variety of 

 materials, including iron, steel, brass, muntz metal, aluminium, 

 bronze and New South Wales timbers. It was devised by Mr. 

 P. Y. Appleby and was sent to me by Prof. Kennedy. It consists 

 of a lever by means of which the elongations in the test specimen 

 are multiplied from 100 to 200 times according to the degree of 



