176 Dr. Tyndall on the Progress of the Physical Sciences: 



of the current through both spirals were the same and when they 

 were opposite, compels the conclusion, that, in the position above 

 described, the wires exercise no influence upon each other, which 

 result was indeed anticipated. The spirals were now set nor- 

 mally opposite, and brought within a line of each other. In the 

 following experiments the combinations of the spirals were essen- 

 tially the same as in the former ; the observations differing merely 

 therein, that for the first vertical column, under the head ' Tem- 

 perature/ the thermometer stood nearest to the inner coating of 

 the battery, while for the second column the spirals were nearest 

 to the same coating*. 



A comparison of these results with those first obtained shows 

 that an alteration of the current takes place when one portion of 

 the connecting wire is brought near to another and parallel to it. 

 In order to express the result in a brief manner, let the connecting 

 wire be conceived to be of three different shapes ; stretched out 

 straight, bent into the form of a U, and bent into the form of 

 an N (the two parallel sides of the latter being brought very 

 near each other). The discharge of a battery through the N form 

 gives the feeblest result, that through the U form the strongest, 

 the current through the straight wire being intermediate between 

 both. In general the modification of the current is so incon- 

 siderable, that in common experiments with the battery it may 



