190 



Scientific Proceedings, Royal Dublin Society. 



round one in the centre, the circuit being so arranged that the electric 

 current passed through the five wires in the same direction, that is, the 

 wires were in series, and the return circuit was at a distance of 2 metres. 



The strength of the transverse magnetic field in the gaps was proportional 

 to the total current through the wires. By plotting the values of the current 

 as abscissae, and the corresponding values of the field as ordinates, and if a 

 straight line be drawn from the origin to the point corresponding to current 

 = 50 amps. (10 amperes in each wire) and magnetic field = 139 units, then 

 all the intermediate points will lie on that line. 



The same nickel wire was used for the transverse fields as for the 

 longitudinal fields, and in order to keep the wire in the middle of the slot in 

 the iron tube, and to prevent its moving towards the face of the slot when a 

 magnetic field was applied, there were smooth strips of wood — well lubricated 

 on the inner faces touching the wire — fixed at both sides of the wire along 

 its whole length. This prevented any lateral motion of the wire and at the 

 same time did not interfere with the slight longitudinal motion produced 

 during the experiment. With transverse fields the wire was tested when 

 under two constant loads of 10 5 and 2 x 10 s grammes per sq. cm.; the same 

 working load of 2 kilos, was also employed. The results for the smaller load 

 are given in Table II and are shown as curves in Fig. 2. 



Table II. 

 Load = 10 5 grammes per sq. cm. 



