224 Dr Fyfe on the Comparative Value of different kinds of 



consequently, the value of these coals for yielding gas ; and, 

 also, in trying whether or not gas is affected by its transit in 

 the street pipes, I have thought it proper to lay the results of 

 these trials before the society. The subject is, in many points 

 of view, of importance ; and I trust, that what I have now to 

 communicate will not be devoid of interest to a Society, the 

 chief object of which is the promotion of our arts and manu- 

 factures. 



I. On the Comparative Illuminating Power of Oas from different Coah, 

 and the consequent value of these Coals for the Manufacture of 

 Gas. 



The coals on which the trials were made, were those from Les- 

 mahago, of which there were two kinds, called the Duke's and 

 Ferguson's, the Monkland, the Knightswood, and Skaterig 

 coals, from the west of Scotland ; the Wemyss and Torryburn 

 coals from Fifeshire, and the Arniston, the Dryden, and Mar- 

 quis of Lothian'^s coal, from the neighbourhood of Edinburgh. 

 Of the last, there were two kinds, marked A and B, the for- 

 mer being that generally used by the Gas Companies here. 



The above coals were first subjected to analysis, with the 

 view of ascertaining the per centage of gas, of coke, and of 

 ashes, and also the specific gravity » The following was the 

 result : 



