1903]. Stress and Strain in the Cross-section of a Beam. 17 



Table I. — Loads 1 to 1J tons. Cast-iron Beam No. 1. 



Load. 



Scale reading. 



Diffs. 



Mean diff. 



Tons. 



1 -o 

 1-5 

 10 

 1-5 

 1-0 

 1-5 

 1 -o 



110 -o 



103 -9 

 110 -1 



104 -0 

 110-2 

 104 -0 

 110 -1 



♦ 



6-1 

 6-2 

 6-1 

 6-2 

 6-2 

 6-1 



6-15 



Position of instrument, 2nd line from top. Index mark, 50. Eight-hand scale 

 descends when load is increased. 



Results of the Experiments. 



The experiments for each load were carried out in the manner 

 described above, and the load was at first advanced by J-ton intervals. 

 Some difficulty was experienced, however, in obtaining satisfactory 

 results for the first J ton, and ultimately the zero readings were 

 rejected and a series taken between \ and \ ton. This is summarised 

 in Table II. 



Table II.— Load £ to J ton. 



Number of 



Distance from 



Mean scale 



Lateral strain 



mark. 



centre. 



differences. 



in specimen. 



1 



3-175 



4-68 



3 -92 x 10- 5 



2 



1-905 



3 24 



2 71 



3 



635 



1-20 



1-00 



4 



o-oo 



o-oo 



0-00 



5 



- -635 



- 1-10 



- 92 



6 



- 1 -905 



- 2-95 



- 2-47 



7 



- 3 -175 



- 4-87 



- 4-08 



The minus sign denotes that the lateral strain was a contraction. 



The values, of course, refer to the elastic state of the bar only, 

 permanent set having been removed as far as possible before the 

 readings were commenced, by alternate application and removal of the 

 load. 



The experiments were then continued in an exactly similar manner, 

 the loads being increased by \ tons until 2 tons was reached, and the 

 last set of readings being taken between 2 and 2J tons. 



Fracture took place at 2 '46 tons. It showed sound material and 

 occurred about 1 cm. from the middle of the span. 



vox,, lxxiii. C 



