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XVII. — On the Composition of the Gas produced by the 

 Joint Distillation of Tar and Water at a high temperature. 

 By John Leigh, Esq., M.R.C.S., F.C.S., &c. 



Read January 21, 1851. 



Some time ago a process was. brought under the notice of 

 this Society by Mr. White, for the manufacture of illumi- 

 nating gas from resin, tar, and other matters. The process 

 had been made the subject of a patent, and was, I pre- 

 sume, brought before the Society on its scientific merits. 

 It is not usual, I believe, for societies like this to receive and 

 to discuss communications of patented processes for manu- 

 factures of any kind ; but as it was supposed that an impor- 

 tant scientific principle was involved in this method of Mr. 

 White's, it was, I presume, on that account allowed to be 

 received, and has on several occasions been very freely 

 discussed in this room. As somewhat different opinions 

 appear to have been entertained respecting it, I thought 

 the communication of the results of a very carefully made 

 analysis of the gas produced where tar was the material 

 employed, might be interesting to the Society, and perhaps 

 throw some light on the process itself. 



It has long been known that when melted resin, or resin 

 oil, is caused to fall upon, or trickle over, an extensive 

 heated surface, that good gas is produced. A company 

 was formed in London several years ago, for the manufac- 



