510 



Prof. A. Ewing. 



[June 10, 



VII. " On certain Effects of Stress on Soft Iron Wires." By J. 

 A. Ewing, B.Sc, F.R.S.E., Professor of Mechanical Engi- 

 neering in the University of Tokio, Japan. Communicated 

 by Fleeming Jenkin, F.R.S., Professor of Civil Engineering 

 in the University of Edinburgh. Received May 24, 1880. 



The following is a preliminary notice of some of the results of ex- 

 periments which are still in progress. As I hope to publish later a 

 detailed account of the whole investigation, it is unnecessary to 

 describe here, in more than brief outline, the apparatus which has 

 been employed. 



The wires experimented on were of soft Japanese iron, drawn in 

 Japan, and annealed shortly before being tested. Each wire was 

 stressed separately by being hung vertically from a strong frame, 

 a tank capable of holding 100 kilos, of water being attached to 

 the lower end of the wire. The weight of the empty tank was 

 balanced, so that the stress on the wire was due only to the weight of 

 water in the tank. The tank was circular and of uniform diameter 

 from top to bottom, and the stress on the wire was therefore propor- 

 tional to the height of water in the tank. This height was recorded 

 on a sheet of paper drawn along by a float, which rose as the water 

 was run in. A pencil travelled transversely across the paper through 

 distances proportional to the elongation of the wire. In this way a 

 continuous diagram was automatically drawn, showing the relation of 

 the strain or elongation to the stress from zero stress up to the 

 breaking point. 



Fig. 1. 



-Stress increased uniformly up to breaking point, at the rate of 1 kilogramme in 15 



seconds. 



Siress on wire in kilogrammes. 



