1903.] Stress and Strain in the Cross-section of a Beam. 23 



The method of applying the load was similar to that described in the 

 paper quoted above, so that the lateral strains do not include that 

 due to permanent set. The specimen was not tested to fracture. 



It will be seen that the elastic lateral strain is proportional to the 

 stress. The ratio may be expressed 



Lateral strain per kilogramme per square centimetre = 20*66 x 10~ s . 



The compression piece was cylindrical in shape, 2*436 cm. in 

 diameter, and about 7*5 cm. high. The measurement of change of 

 diameter was made about the middle of the specimen, in order that 

 the effects of any suppression of the dilatation at the ends might be 

 avoided. 



The load was applied exactly as in the case of the tensile piece. 

 Table VII (Appendix) contains the results. The total magnification 

 was 3002. 



The ratio of stress to strain is not quite independent of the 

 stress. Near the origin the lateral strain per kilogramme per square 

 centimetre = 20*91 x 10~ s . 



In conjunction with my colleague, Mr. E. L. Watkin, M.A., I have 

 made a large number of experiments on these stress-strain relations for 

 cast-iron. "We hope to publish an account of them shortly. Some of 

 the specimens used were cast at the same time and from the same 

 ladle as the second beam described in this paper. 



In Table VIII (Appendix) are embodied the results obtained from 

 two of these, the particular ones chosen giving average and fairly 

 representative values. The tension piece was 1*958 cm. in diameter, 

 and the compression specimen 2*499 cm. diameter and 7*5 cm. high. 



For comparison with the wrought-iron beam the relations were 

 obtained from separate specimens of similar material. 



In the case of tension the lateral strain has been found to be directly 

 proportional to the stress when within the elastic limit, and the experi- 

 ments described in a previous paper* gave, for the material in question, 

 the value 13*80 xl0 _s for the lateral strain per kilogramme per 

 square centimetre. 



The wrought-iron compression specimen was similar to those of cast 

 iron, 2*404 cm. diameter and 7*5 cm. high. The load was applied by 

 \ ton intervals up to 2 tons, and then by tons to 4 tons. The lateral 

 dilatations were not quite proportional to the stresses applied. The 

 results are given in Table IX (Appendix). 



The relations between stress and lateral strain for all three cases 

 are shown graphically in the curves of fig. 6. The origin of the curve 

 for comparison with Cast-iron Beam No. 2 is displaced to the right a 

 distance of 10 x 10 -5 unit. 



* See £ Phil. Mag.,' Sixth Series, vol. 6, No. 34, p. 417. 



