Riess on Electric Currents of the First and Higher Orders. 177 



be entirely neglected. To place the fact beyond doubt, we see 

 that it is necessary to place 107 feet of a current 119 feet in 

 length within a line of each other, by winding them into two 

 spirals, the most distant parts of each of these being not more 

 than a foot apart. In the wire screws, used so frequently in the 

 circuit for the sake of sparing room, the distance between two 

 windings is much less than the diameter of the screw ; hence a 

 wire wound into this form must, as in the case of the N wire, 

 principally weaken the current. 



In the series of experiments given above, the spirals were 

 united by a copper wire 29 inches long and ^ths of a line in 

 thickness. The measured currents bore nearly the following 

 proportions to each other : — 



Without the action Current in same direction. Current in Opposite directions, 

 of the spirals. N combination of the spirals. U combination of the spirals. 

 100 89 106 



The connecting wire was exchanged for one of 39i inches in 

 length and ith of a line thick. Out of twenty-seven observa- 

 tions, the following numbers were found for the respective 

 currents : — 



100 91 106 



Finally, a steel wire, 34^- inches in length and /.rths of a line in 

 thickness, was introduced, and with this I obtained the following 

 numbers : — 



100 88 109 



The phenomenon is therefore independent of the retarding value 

 of the wire which unites the spirals ; for here we have very dif- 

 ferent values of retardation, but currents of almost the same 

 proportions. In all these cases the increase of the current is less 

 than the diminution, which therefore must not be regarded as 

 an accidental circumstance. 



The result established may be thus expressed : — 

 Two portions of the connecting wire of a battery, which run 

 closely parallel, act upon each other. The current will be weakened 

 by lids action when its two parallel portions move in the same 

 direction, and strengthened when they move in opposite directions. 



The secondary current. — To excite a secondary current, two 

 wires must be placed near each other; the most convenient way 

 of effecting this being to wind them into spirals cither as discs 

 OT cylinders (we shall call them in future induction-discs, or in- 

 faction-cylinders). From former experiments the author was 

 led to conclude, that the heating in the thermometer was pro- 

 portional to the number of coils; but this is only approximately 



Phil. Mag. S. 4. Vol. 3. No. 17. March 1852. N 



