124 



Mr. G. Gore on the Rotations 



[Dec. 9, 



just above the top end of the vertical iron axis. By supporting this 

 apparatus as the axial wire in the previous experiment, and passing the 

 current, rotation occurred, showing that the chief use at least of the coil- 

 current was to impart longitudinal magnetism to the axial wire, and that 

 the rotation was not simply due to any reaction between the coil and that 

 wire. Reversing the direction of the current did not reverse the direction 

 of rotation. In another experiment similar to this, I formed about 12 

 centims. in length of the middle part of the axial wire of copper instead 

 of iron, and obtained similar rotation ; but as copper is only slightly 

 capable of acquiring longitudinal magnetism from a coil-current sur- 

 rounding it, a precisely similar apparatus having an axial wire composed 

 entirely of that metal would not rotate. 



These experiments and the following ones produce a striking effect in 

 a lecture, because the rotation appears to be produced without reaction 

 of the moving part of the apparatus upon any external or fixed body. 



6. To determine whether the longitudinal element of the coil- current 

 obtained by obliquity of winding of the- wire might be substituted for 

 the longitudinal current through the magnet, I took an iron wire 13 

 centims. long and 1*7 millim. diameter, sharp-pointed at its lower end, 

 soldered near to that end one extremity of a cotton- covered copper wire 

 1*7 millim. in diameter, coiled the latter in one direction to the middle 

 part of the iron wire, then reversed the direction of winding and coiled 

 to the other end of the iron, and terminated the coil by a little brass cup 

 just above the upper end of the iron wire as before. By supporting this 

 apparatus as in the previous experiments, and passing the current, rapid 

 rotation took place, proving that a longitudinal current in the iron itself 

 was not necessary. 



7. To ascertain whether the longitudinal element of the current was 

 essential to the motion, I constructed a similar appa- 

 ratus to the last, but instead of attaching the upper 

 end of the coil wire direct to the brass cup, I continued 

 the copper wire vertically downwards to the bottom of 

 the coil, to neutralize the effect of obliquity of winding; 

 then carried it outwards and upwards in the form of a 

 large rectangle 5 centims. distant from the coil and on 

 to the mercury-cup, as shown in fig. 1. On passing 

 the current rotation occurred freely, showing that the 

 longitudinal current was not essential to the motion. 

 This experiment, and that described in paragraph 4, ap- 

 pears to prove that the rotation is not an effect of any 

 obliquity or spiral arrangement of the axes of the magne- 

 tized iron molecules with regard to the axis of the wire, produced by the 

 combined action of the transverse and longitudinal elements of the 

 current in the coil, because the latter element was neutralized, but that it 

 is an effect of the tangential poleless magnetism in the fixed wires above 



Eg. i. 



