hitelligence and Miscellaneous Arlicles, 541 



that the changes taking place on the surface of the leaf cause it 

 to assume a positive state of electricity, negative electricity being 

 given oif to the surrounding medium. The direction of the current 

 is not affected by the presence or absence of light, but a greater 

 quantity of electricity is set in motion during the day than in the 

 night.— Oc^ 26. 183*7. 



ON THE DECOMPOSITION OF WATER BY THERMO-ELECTRICITY. 

 BY MR. F. WATKINS. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



As the decomposition of water by thermo-electricity is an experi- 

 ment which must interest all persons engaged in philosophical 

 pursuits, I venture to trespass on your pages to explain how it 

 may be rendered visible in a marked and distinct manner, which, 

 until now, I believe, has not been accomplished. 



We learn from the Bibl. Univ., vol. li. p. 337, that in 1833 

 M. Botto of Turin, succeeded in decomposing water, and acid and 

 saline solutions by means of thermo-electric currents, making use of 

 metallic elements formed not of a series of bars, but of a great 

 number of platinum and iron wires placed alternately. The elec- 

 trodes in his decomposing apparatus were oxidizable metals. 



M. Aug. De la Rive informed me, last autumn, that he had re- 

 peated M. Botto's experiments, and noticed a few minute bubbles 

 of hydrogen given off at the proper electrode. A communication 

 commences in the Lond. and Edinb. Phil. Mag., No. 62., May 1837, 

 p. 415, from Professor Wheatstone, informing us that Professor 

 Linari of the University of Siena had, in 1836, succeeded in decom- 

 posing water with a Nobili's thermo-electric pile ; that wires were 

 emi)loyed having oxidizable electrodes, and that hydrogen was sen- 

 sibly evolved at one of them. 



The escape of a few minute hydrogen bubbles at the proper elec- 

 trode is sufficient to stamp the fact, on the mind of the philosopher, 

 that chemical decomposition has been effected ; but to illustrate the 

 phsenomena enlarged effects are required, which cannot be obtained 

 either by M. Botto's, or M. Linari's apparatus. By adopting the 

 plan I shall now proceed to point out, streams of the two liberated 

 gases, consequent upon the decomposition of water when platinum 

 electrodes are used, may be seen and collected in the ordinary 

 way. 



I employ a massive thermo-battery with pairs of bismuth and 

 antimony, a small apparatus for the decomposition of water of the 

 ordinary description, and an electro-dynamic helical apparatus. 

 The primary coil of wire is 90 feet long, and when the thermo- 

 battery current simply pervades this coil, I do not notice any disen- 

 gagement of the gases ; but so soon as the contrivance for making 

 and breaking battery contact is put in action, then an evolution of 

 the gases takes place, while at the same time powerful shocks are 

 received from the secondary coil of ^vire 1500 feet long. 



I remain, Gentlemen, yours, &c. 

 5, Charing Cross, March 3, 1838. Francis Watkins. 



