NO REACTION BETWEEN A MAGNET OR VOLTAIC CURRENTS AND LIGHT. 7 



ment and light, some derangement would be seen in the diffracted fringes when the 

 current passed ; but none such was observable. 



14. Again, two wires were so adjusted that they could be made to approach or re- 

 cede from each other by a screw movement, and voltaic currents be passed in either 

 direction, up or down them, conjointly or separately ; when they were within the rlrth 

 part of an inch, the fringes they produced were very perceptible, but the passage of the 

 current caused no alteration whatever. These experiments were also repeated in ho- 

 mogeneous light, with the same results. 



15. A hollow prism, a b (Jig. 3, pi. 1), for containing transparent but imperfectly 

 conducting liquids, was traversed by a voltaic current from the battery, c z, by means of 

 platina wires, e e, one extremity of each of which went to the bottom of the liquid, and 

 the other dipped into the mercurial cups of communication, d d. A ray of light, f, 

 passed through the prism, and was refracted on the screen, g I, or viewed by a glass. 

 Some of those lines which traverse the spectrum were at times visible ; but neither 

 these nor the spectrum itself suffered any perceptible alteration during the passage of 

 ihe current. 



16. Some philosophers have pointed out the different degrees of temperature which 

 Sir W. Herschel detected in different parts of the prismatic spectrum, as analogous to 

 that increase of temperature which takes place in the cells of the voltaic battery, as we 

 proceed from the negative to the positive pole. Hence, they have supposed that each 

 end of the spectrum was in an opposite electrical state. With the analogy I have 

 nothing to do ; but to ascertain whether the deduction from it is founded in fact, I 

 made this experiment I received into a tube, a b (Jig. 4, pi. 1), filled with acidu- 

 lated water, the whole of the prismatic spectrum cast by an equiangular prism of Eng- 

 lish flint glass, in that part, c, which was covered by the violet ray ; I immersed one 

 wire, e e e, of a. galvanometer, arranging the other \vire,ff, in that part, d, which re- 

 ceived the red ray. Alternately placing and withdrawing the arrangement from this 

 position, it was to be expected that either a continuous current or a wave of electricity 

 would pass along the galvanometer wires, producing either a permanent or transient dis- 

 turbance. I was not able, however, to notice such an effect ; and suspecting that, if 

 any electricity was developed, it might be of such low intensity as to be unable to pass 

 through acidulated water, I repeated the experiment, using, instead of the tube of wa- 

 ter, a piece of polished tin, in the shape of a parallelogram, three inches long and one 

 broad, to each end of which the galvanometer wires were soldered ; but the results were 

 still negative. 



17. The general termination of these experiments would lead us to suppose, that if 

 there be any reaction between galvanic or magnetic currents and solar light, they are of 

 such a nature as to forbid repetition in latitudes as far south as 35. 



