Riess on Electric Currents of the First and Higher Orders. 183 



which excites it excite at the same time a second secondary in a 

 well-closed circuit, a case to which the reader's attention has 

 heen directed in a note; hence the possibility of lessening the 

 supposed tertiary current by the intentional formation of a second 

 tertiary. This was effected as follows :— The primary circuit 

 contained a large induction-disc ; the secondary circuit a similar 

 one, the wire of the thermometer and 53 feet of copper wire, 

 which was first stretched out, and afterwards exchanged for a 

 plane or a cylindrical spiral formed from the same length of 

 wire. Parallel to this plane or cylindrical spiral, and at about a 

 line distant from it, ran another spiral, which we shall call the 

 tertiary spiral; the secondary current was first measured while 

 the tertiary spiral remained open, and afterwards when it was 

 closed by 23 feet of copper wire. The following are the results :- 



In the secondary circuit 53 feet of copper wire. 



100 



As cylindrical spiral. 



74 



Tertiary spiral 

 closed. 



OS 



As plane spiral. 



OS 



Tertiary spiral 

 closed. 



95 



The secondary current, which, with a stretched-out we, had 

 the value of 100, was weakened to 74 when the same length oi 

 wire was wound to the shape of a cylindrical spiral, and to 60 

 when its shape was that of a plane spiral. But on permitting 

 of the formation of a tertiary current by closing the ends ot the 

 tertiary spiral, the current rose to 98 and 95 in these respective 

 cases Thus the production of a second tertiary checked, as 

 conjectured, the formation of the one to which the weakening of 

 the secondary was due, a striking increase of the latter being 

 the consequence. It was proved by other experiments that the 

 strengthening of the secondary current by the^U-form of its 

 wire is also due to the formation of a tertiary current in the 

 mass of the latter. . . . „ 



Following up the system of procedure indicated in the tore- 

 troinfl pages, M. lliess has subjected currents of the third, fourth, 

 ;unl 'fifth orders to experimental examination. The laws of ac- 

 fcion in each respective case are precisely the same as those which 

 apply to the secondary current, and which we have just described. 

 The tertiary reacts upon the secondary 111 a manner similar to 

 the reaction of the secondary upon the primary; in tact the 

 relation of any given current to that of the next higher order is 

 ■B a \\ reipecta that of primary to secondary; the tertiary cur- 

 rent is modified by changing the shape of its wire, being 



