DECOMPOSITION OF WATER BY HEAT. 317 



quent experiments, I trust, abundantly negative this supposi- 

 tion, yet as this was my first successful experiment on this 

 subject, and is per se an interesting and striking method of 

 showing the phenomenon of decomposition by heat, I will 

 mention a few points to prove that the phenomenon could not 

 be occasioned by electrolysis. 



To account for it by electrolysis, it must be supposed that 

 the wire offered such a resistance to the current that this 

 divided itself, and the excess of voltaic power passed by the 

 small portion of water which trickled down, instead of by the 

 wire. 



In the first place, the experiment was performed with dis- 

 tilled water, and only two cells of the battery employed, which 

 will not perceptibly decompose distilled water. 



2. No decomposition took place until the instant of ignition 

 of the wire, though there was a greater surface of boiling 

 water exposed to the wire before than after the period of 

 ignition. 



3. A similar experiment was made, but with the wire 

 divided in the centre so as to form two electrodes, and the 

 water boiled by a spirit-lamp ; here the current had no wire to 

 conduct any part of it away, but the whole was obliged to 

 pass across the liquid, and yet no Fig. 6. 

 decomposition took place, or if there 



were any it was microscopic. 



4. When, instead of oil, distilled 

 water was used in the outer vessel,* 

 even the copper wires, one of which 

 would form an oxidable anode, gave 



no decomposition across the boiling water outside, while the 

 ignited wire inside was freely yielding mixed gases. 



5. To prevent the water from being the shortest line for the 

 current, I repeated the experiment with a perfectly straight wire 

 (fig. 6). The result was precisely the same ; but the experi- 

 ment is more difficult, as a certain length of wire is neces- 



* Jan. 8. I have since found that the exterior tube of oil or water may be 

 dispensed with in this experiment, as the water which trickles down prevents the 

 fusion of the glass, 



