Equipotential Lines of an Electric Current. 133 



ing that the transverse effect would prove to be less marked 

 near the end than in the middle of a metal strip. Similar rea- 

 sons led me to suppose that the effect would, cet par., be less 

 in a short strip, No. 16, than in a long strip, No. 15, both 

 being of F. C. R. steel. Strip No. 15 was like those already 

 described but without any slit: Strip No. 16 was cut from 

 the middle of a strip like 15 and was of about the same 

 width, but only l\L cm or l*2 cm long. Fearing that soldering con- 

 nections to the ends of so short a strip as No. 16 would change 

 the character of the strip throughout, , I used no solder with 

 Nos. 15 and 16, but made connection with their ends by means 

 of strips of lead pressed firmly down upon them by means of 

 stout clamps. For No. 16 each of the lead strips was made 

 about l cm long and as wide as the steel in order to give the 

 main current, coming in from the connecting wires, oppor- 

 tunity to spread and become parallel to the edges of the strip 

 before entering the steel. The part of No. 16 not covered by 

 the lead was about 5 mm long. Whether the space not touched 

 by the lead was longer, cannot be ascertained, but the extreme 

 length possible was, as the dimensions already given show, 

 about l*l cm . Lead was used for making connections partly 

 because its softness made a good contact probable and partly 

 because, lead showing very little or no transverse action of the 

 sort under examination, its use would practically limit this 

 transverse action to the steel strip. 



The transverse connections were made, as with the other 

 steel strips mentioned in this article thus far, by means of two 

 stiff German-silver springs, each touching the steel at one point. 



The considerations which led to the experiments, with 15 and 

 16 were nearly as follows : The transverse action, whatever 

 may be its explanation, makes the equipotential lines run ob- 

 liquely instead of straight across the strip in which it occurs. 

 If such a strip were short and were joined at each end to 

 another strip in which the same action does not occur, the 

 direction of the equipotential lines in each strip near the junc- 

 tion should be affected by the proximity of the other strip, 

 so that lines in the inert strip would not run perfectly straight 

 across and lines in the active strip would run less obliquely 

 than they otherwise would. If a strijD were short, like No. 16, 

 this modification in the direction of the lines might be appar- 

 ent throughout its whole length, so that the transverse action 

 in a short strip might appear less powerful than in a long strip.* 



May 23, 1885, Nos. 15 and 16 were tested, No. 16 first, then 

 No. 15, finally No. 16 again. These tests were by no means 

 accurate, but they left no doubt that the apparent transverse 



* See also, upon this point, Ettingshausen and Nernst in the Beibldtter zu 

 den Annalen der Phys. u. Cham., Band xi, Stuck. 5. 



