288 Mr. W. Herapath on the 



tube C. A stream of common air was made to act on the 

 metal through the perpendicidar tube B ; it now glowed and 

 continued to do so as long as both streams were continued ; 

 when either failed, it immediately cooled ; while the metal 

 continued red hot, there was no inflammable gas issuing from 

 the tube C, while water rapidly condensed within it. 



In these experiments, the bulb containing the platinum was 

 placed in water at the respective temperatures of 60°, 70°, 80°, 

 90°, 100°, and 98° (blood heat); at the first four no effect 

 was observable, while it was at the last two. After 130 cvibic 

 inches of hydrogen had passed, the water in the tubes was 

 driven off'by heat, and the appai'atus weighed; it had lost 'OSgr,, 

 which I attributed to accident ; but to prove it, I passed 1 30 

 cubic inches moi'e, and upon reweighing there was no further 

 diminution. 



Exp. 4. The bladders were now changed so that the pla- 

 tinum was in an atmosphere of common air; there was no action 

 at any temperature; but as soon as hydrogen was passed down 

 the tube B, and the platinum was heated to 98° or 100°, the 

 gases were condensed as before. 



Exp. 5. Coal gas mixed with common air was next passed 

 through the tube B (A being stopped) ; it caused the metal 

 to glow, but not until the temperature was much increased. 

 I did not ascertain the exact point, as I consider that it would 

 vary with different proportions. 



Exp. 6. The tube B was then connected with the gas blow- 

 pipe and a fine stream admitted, taking care to avoid explo- 

 sion or inflammation; at 100° it glowed as before. If in ei- 

 ther of the foregoing cases any moisture was present upon the 

 metal, no action took place ; whereas the combination was ef- 

 fected more readily and at a lower temperature, when the ex- 

 periment was repeated a second time within a short time after 

 the first, which I suppose was owing to the platinum being a 

 very bad conductor of caloric, and consequently not cooling 

 to the temperature of the surrounding medium within that 

 time. I found that the same platinum might be used for any 

 length of time, with the precaution of using it dry. 



Imagining that the effect might be electrical, I placed some 

 of the metal in a platinum foil cup on Bennett's electrometer ; 

 it glowed in the parts not adjoining the foil, but no signs of 

 electricity were observable. 



To try if it was owing to the nonconducting power, I passed 

 a stream of the gases upon asbestus, which is a nonconductor 

 of caloric and finely divided (but fibrous instead of spongy) ; 

 but there was no action. 



I tried 



