i 



^R, HENRY ON COMBUSTIBLE GASES, 73 



POSTSCRIPT. 

 SIpGC the preceding: pages were written, I have examined '^^^ S^^ from 



: ^,r 11-it • coal appears W 



a trefti portion or the gas from coal, obtained by very cautious g^^p^ ^jtlj ^^^ 

 diftillalion, with a view to afcertain whether any olehant gas m. acid gas to 

 can be procured from that fubflance. Of this gas five rneafures ^^^^^-^^^ ^^ ^1^ 

 mixed with five of oxygenized muriatic acid, were reduced togas, 

 qine; from which it (liould appear that the gas from coal may 

 poffibly contain -^^ of ole/iant gas. The produflion of oil, 

 however, was not fo manifeft as in other inftances; and I 

 judged it to have happened chiefly becaufe an iridefcent film 

 was vifible on the furface of the water when held between the 

 eye and the light. 



I am enabled a!fo, by a letter received this morning from a Hiftoryof Mr. 

 friend who is well acquainted with the progrefs of Mr. Mur- Muidoch's ex- 

 doch^s experiments, in anfwer to fome queries from me, to gWing light by 

 Hate fpecifically the grounds of that gentleman's claim to the g^^s from pit- 

 important application of coal as a fource of artificial light. — 

 This I cannot do better than by an extract from the letter. 

 " ** In the year 1792, at which time Mr. Murdoch refided at 

 Redruth in Cornwall, as Boullon and Watts principal agent 

 and manager of engines in that county, he commenced a fe- 

 ries of experiments upon the quantity and quality of thegafes 

 contained in different fubftances. In the courfe of thefe, he 

 remarked, that the gas obtained by difiiilafion from coal, peat, 

 wood, and other inflammable fubfiances, burnt with great 

 brilliancy upon being fet fire to; and it occurred to him, that 

 by confining and conduding it through tubes, it might be em- 

 ployed as an economical fubftitute for lamps and candles. The 

 diftillation was performed in iron retorts, and the ga^ con- 

 <judled through tinned iron and copper tubes, to the diftance 

 of 70 feet. At this termination, as well as at intermediate 

 points, the gas was fet fire to, as it patTed through apertures 

 of different diameters and forms, purpofely varied with a view 

 of afcertaining which would anfwer beft. In fome, the gas 

 iflued through a number of fmall holes, like the head of a wa- 

 tering pan ; in others it was thrown out in thin long Iheets, and 

 again in others in circular ones, upon the principle of Argand's 

 lamp. Bags of leather and of varnifhed filk, bladders, and 

 veffels of tinned iron were filled with the gas, which was fet 

 fire to, and carried about from room to room, with a view of 



afcer- 



