THE THEEMO-ELEOTRIC EFFECTS OF LONGITUDINAL STRESS IN IRON. $1 



neiiled soft iron, were all of the type given by Dr. Cohn, and can be 

 represented by Fig.- 3 or 4, PI. I. Being- at the time unacquainted 

 with Prof. Ewing's paper, it, cost, me much labour to establish the fact 

 that to get a curve of Prof. Ewing's type, which can be represented by 

 Fig. 6, PL I., it is necessary to pull the annealed soft iron wire beyond 

 its limit of elasticity. This, however, led me to trace the manner of 

 transformation of the thermo-electric curve, as the range of loading 

 and unloading is progressively extended np to and beyond the limit 

 of elasticity. 



§ 8. To illustrate the subject of the last paragraph, one of 

 my experiments may be here cited. The object being sooner attained 

 with a thinner piece of wire, one of soft iron 064 m.m. in diameter 

 was tested. It was carefully annealed in the air witli Bunsen flame 

 three times, — twice with a weight which served the purpose of making 

 the wire straight and finally once after the weight had been removed. 

 The results obtained with the above wire are given in the following 

 tables, which are also graphically represented in Figs. 1-6, PI. I. 

 The cycles of loading and unloading were in the order : (1) — 3 — 0, 

 (2)0 — 6 — 0, (3) — 8 — 0, (4) — 10 — 0. The leaden weights 

 by means of which longitudinal tension was applied to the wire were, as 

 before mentioned, each one kilogramme in mass. Each cycle was gone 

 through twice, for I considered that the readings in the second would 

 be nearer than those in the first to the perfectly cyclic state of changes 

 for the range of loading and unloading. The cycles ought to be repre- 

 sented by one continuous curve, yet to avoid confusion, they are so 

 grouped that one of the pair in each figure refers to the second process of 

 loading and unloading, while the other corresponds to the next con- 

 secutive cycle in which the range of loading was extended (the former 

 in full lines and the latter in dotted lines). The curves are all drawn 

 after Prof. Ewing, that is to say, the horizontal axis is the axis of 



