7^ 



MR, PFNR'X ON COMBUSTIBLE GASE5. 



gen gas ; for 1 find that the carbonic oxide is not expanded by 

 eledtrica! difcharges, which would alTuredly happen if the car- 

 buretted hydrogen were one of its conftituents, or accidentally 

 mixed with it. 

 Elucidation of To return to the thjeory of lamps, &c. it is proved by the 

 the theory of preceding experiments, that the fubftances ordinarily em- 

 *^?h c» ployed as fources of artificial light, viz. oil, tallow, and wax, 

 afford when fabmitted to an increafed temperature, much oIe» 

 fiant gas; and it has been juftly obferved by the editor of this 

 Journal (4to feries I. 71) ** that the wick of a lamp or candle 

 furrounded by flame is exa6ily in the fituation of a body ex* 

 The oil &c. is po^'^d to deftru61ive diftillation in a clofe velfel." In this cafe 

 decompofed in the feries of capillary tubes compofing the wick, ferve perhaps 

 ^ ^^^ ' precifely the fame office as a tube horizontally difpofedina 



heated furnace, through which an inilammable liquid is tranf- 

 mitted. The fuel previopfly melted, is drawn up into thefe 

 ignited capillary tubes, and there refolved into olefiant and 

 •■^into olefiant carburetted hydrogen gafes, from the combuftion of which 

 and carburetted gafes, and not r^Cfcly of a condenfible vapour, it appears to 

 whlcKe^S ^^ ^^^^ ^^^^ illumination chiefly proceeds. Hence it is not im- 

 turned. Whence probable, that the proportion of olefiant gas and hydrocar- 

 thefitnefsof any j^^j.^. obtained by the diftillation of any fubftance, will be a 



fuel to give lu- . ' . , "^ . . 



ininous flame tolerable meafurc of its fitnefs for affording light. In diflil- 

 TTiay be known lations of this k^nd, however, the degree of heat is of con- 

 tive diftilla- fiderable moment, for I have found that the olefiant gas may 

 tion. be obtained or not, at pleafure, during the decompofition of 



ether, alcohol, oil, &c. by varying the temperature to which 

 the containing vefTels are expofed. 

 , f fA In the gafes from coal, peat, and wood, though thefe fulv 



coal, &r.- though ftances yield no olefiant gas, the defect is compenlated by an 

 they offered no inflaraijiable vapour, diffiifed through them when recent, and 

 afford much which is eyep not removed by.pafTing through a fmall quantity 

 jight by an in- Qf ^ater. Gas from coal, however, which had flood oyer 

 vapour^when water upwards of a month, I have found burns with confi- 

 Tecent. derably impaired brilliancy, though flill with a far more denie 



and bright fiame than hydfogen gas, or the gas from char- 

 coal. , 

 Manchejter, May ^^ IS 05, 



TOST. 



