3i8 ^EXPERIMENTAL INVESTIGATIONS. 



sary, the sealing is more troublesome, and the size of the 

 bulb is much more difficult to adapt to the production of 

 steam in exactly the requisite quantity : the straight wire 

 being more suddenly extinguished and more easily fused : 

 with careful manipulation, however, it succeeds equally well 

 with the former experiment. 



I might add other experiments and arguments, but I believe 

 when the remainder of this paper has been read, that the above 

 will be thought scarcely necessary. 



I now directed all my efforts to produce the effects by heat 

 alone without the battery. I will mention a few of my un- 

 successful attempts, as it will save trouble to future experi- 

 menters. I sealed a platinum wire into the extremity of a 

 curved tube, filled the latter with water, and applied a strong 

 heat by the blowpipe to the projecting end of the wire, hoping 

 that the conducting power of the platinum, although inferior 

 to that of most other metals, was sufficiently superior to that 

 of glass to enable me to ignite the portion of the wire within 

 the tube, and thus surround it with an atmosphere of steam ; 

 the water, however, all boiled off from the glass ; nor could I 

 succeed in igniting the platinum by heat from without. A 

 similar failure occurred when, on account of its superior 

 conducting power, a gold wire was substituted for that of 

 platinum. 



I sealed spongy platinum and bundles of platinum wire 

 into the ends of Bohemian glass tubes, closing the glass over 

 them, and then filling the tubes with water and heating the 

 whole extremity; but the water boiled off from the glass, and 

 the platinum could not be made to attain a full incandescence. 



After many similar trials I returned to the battery, and 

 sought to apply it in a manner in which electrolysis could not 

 possibly take place. I had hoped, as I have above stated, to 

 obtain a residual decomposition of water by masking or dilut- 

 ing the gases by a neutral substance. I therefore tried the 

 following experiment : a tube similar to fig. I was filled with 

 water which had been carefully freed from air by long boiling 

 and the air-pump ; it was then inverted in a vessel of the same 

 water, and a spirit-lamp applied to its closed extremity, until 

 the upper half was filled with vapour (see fig. 7). The wire 



