674 TRANSACTIONS OF SECTION G. 



an axis, including measurement of moment of inertia and moment of momentum, 

 and to study the composition of accelerations and S.H.M. Also apparatus to 

 measure the range of a projectile, the back pressure of a jet of water, the meta- 

 centric height of a ship model, and the horse-power ti-ansmitted by a propeller shaft. 



WEDNESDAY, AUGUST 8. 



The following Papers were read :— 



1. The Central Technical College Lecture Table Testing Machine} 

 By Professor Ashcroft. 



2. The Strength and Behaviour of Dxhctile Materials under Combined 

 Stress, By Walter A. Scoble. 



In former tests of ductile materials under combined stress, either the ultimate 

 strength has been considered or the tensions have been applied so that the distribu- 

 tion was approximately uniform. The experiments were made on bars subjected to 

 bending and twisting to reproduce the irregular distribution of stress occurring in 

 practice, and the yield-point was selected as the criterion of strength. The bars 

 were f inch diameter and 30 inches effective length. The critical bending moment 

 was found to be greater than the yield torque, 2,660 and 2,400 lb. in. and 

 plotting the corresponding bending and twisting moments an ellipse gave the 

 closest approximation to the results. With both loads on there was simultaneous 

 yielding in both ways. The maximum principal stress varied considerably, the 

 maximum shear stress being nearly constant. The results, and those of other 

 experiments, were analysed to determine if the variation of the maximum shear 

 stress was due to a force analogous to friction, or the reverse, proportional to the 

 force perpendicular to the plane of maximum shear. This was found not to be so, 

 the variation in the values of the maximum shear stress probably being due to 

 differences in the shear strength in various directions. 



3. Recent Advances in our Knowledge of Radiation Phenomena^ and 

 their Bearing on the Optical Measurement of TemperatiLve.^ By J. B. 

 Henderson. 



4. Electro-positive Coatings for the Protection of Iron and Steel from 

 Corrosion.'^ By S. Cowper-Coles. 



5. Suction Gas Engine Plants} 

 By Professor W. E. Dalby, M.A., M.Inst. C.E. 



6. Waterproof Boads as a Solution of the Dtist Problem, 

 By Douglas Mackenzie. 



' Published in Engineering, August 2i, 1906. 

 " Published in the Electrician, August 17, 190G. 

 ^ Published in the Engineering Times. 

 * Published in Engineering, August 10, 190G. 



