THE THERMO-ELECTRIC EFFECTS OF LONGITUDINAL STRESS IN IRON. 35 



loaded for the first time, in exhibiting a gradual transferrence of the 

 curves, as a whole, towards the negative side of the axis of load, at 

 the same time an upward extension of the branches corresponding to 

 greater loads, and, lastly, in exhibiting a great change, as above 

 described, when permanent drawing sets in. 



A description of the features of the thermo-electric curve arrived 

 at in the above manner is rendered useless by very full comments on 

 them by Prof. Ewing. (I) 



§ 10. I will now go on to describe my own observations on the 

 effects of loading and unloading at different stages of the thermo- 

 electric curve. (2) Even when the process of loading and unloading is 

 performed within a certain limited range, not exceeding the upper- 

 most limit of the main cycle, the thermo-electric hysteresis manifests 

 itself by causing the "off" branch to lie quite clear of the " on " 

 branch. The curves, closed or otherwise, formed in this w 7 ay will be 

 called minor cyclic curves. 



One of my experiments, given in the following table, made on 

 soft iron wire 054 man. in diameter, may be cited as illustration. 

 For the sake of clearness, the minor cyclic curves are represented 

 separately in Figs. 7, 8, 9, and 10 PI. II, with the main cycle for 

 comparison. They were so chosen as to correspond respectively to 

 the distinct stages of the "on" branch. The first cycle (0 — 1 — 0) 

 which lies quite below the maximum is found to enclose a very small 

 area if any. Once the maximum point is passed, as in the second 

 cycle (0—3—0), the "on" and "off" branches begin to enclose a 

 considerable area, and to show the characteristic features of the cyclic 

 curve, which will be seen quite fully developed in the third minor 

 cycle (0-6-0). 



(1) I.e., §8-11. 



(2) 1. c, § 12. 



