78 SCIESCE AY SHORT CHAPTERS. 



an inch thick and half an inch working length, was held 

 vertically, by metallic forceps at each end, in a barometer 

 tu-be, the upper part of which, containing the carbon, was 

 enlarged to a sort of oblong bulb. A tKick platinum wire 

 from the upper forceps was sealed into the top of the tube 

 and projected beyond ; a similar wire passed downwards 

 from the lower forceps, and dipped into the mercury of the 

 tube, which was so long that when arranged as a barometer 

 the enlarged end containing the carbon was vacuous. 



Considerable difficulty was at first encountered in sup- 

 porting this fragile stick. Metallic supports were not avail- 

 able, on account of their expansion ; and, finally, little 

 cylinders of porcelain were used, one on each side of the 

 carbon stick, and about three eighths of an inch distant. 



By connecting the mercury cup with one terminal of the 

 battery, and the upper platinum-wire with the other, a 

 brilliant and perfectly steady light was produced, not so 

 intense as the ordinary disruption arc between carbons, but 

 equally if not more effective, on account of the magnitude 

 of brilliant radiating surface. 



Some curious phenomena accompanied this illumination 

 of the carbon. The mercury column fell to about half its 

 barometric height, and presently the glass opposite the 

 carbon stick became slightly dimmed by the deposition of 

 a thin film of sooty deposit. 



At first the depression of the mercury was attributed to 

 the formation of mercurial vapor, and is described accord- 

 ingly in the specification; but further observation refuted 

 this theory, for no return of the mercury took place when 

 the tube was cooled. The depression was permanent. 

 The formation of vaporous carbon was suggested by one of 

 the capitalists; but neither Mr. Starr nor myself was satis- 

 fied with this, nor with any other surmise we were able to 

 make during Mr. Starr's lifetime, nor up to the period of 

 final abandonment of the enterprise. 



When this occurred the remaining apparatus was as- 

 signed to me, and I retained possession of the finally ar- 

 ranged tube and carbon for many years, and have shown it 

 in action worked by a small Grove's battery in the Town 



