246 MR. J. LEIGH ON THE GAS 



bon, and yields light carburetted hydrogen and hydrogen ; 

 and, lastly, light carburetted hydrogen deposits its carbon, 

 and escapes as free hydrogen. 



I have had no opportunity hitherto of examining the gas 

 produced by the joint distillation of rosin and water, but a 

 full opportunity of examining that formed by the joint dis- 

 tillation of tar and water ; Mr. White having requested per- 

 mission from the Manchester Gas Committee to make some 

 experiments in connection with an experimental apparatus 

 which the Committee have fitted up at one of the Manches- 

 ter gas stations. This apparatus is on a suflSciently large 

 scale fully to test, in a practical manner, the value of any 

 material required for gas-making ; and, I may observe in 

 passing, that before any cannei or coal is employed for gas- 

 making by the Committee, it is tried in this apparatus. 

 An entire oven of retorts is connected with a distinct set of 

 receiving vessels for the tar and ammonia water, purifiers, 

 washers, and gas-holder, and the gas is measured oiF by a 

 separate meter. Numerous trials are made with the same 

 cannei or coal, and an average of results obtained. The 

 weight and quality of the coke is determined, the amount 

 and specific gravity of the tar and ammonia water, and 

 the volume of the gas produced. The latter is ccHnpared 

 with a standard light, and its relative illuminating power 

 and rate of combustion ascertained. Finally, it is submitted 

 to a full and careful analysis by myself. The relative values 

 of difierent gas-producing materials are determined, both in 

 reference to the economy of their employment and the 

 quality of the light they give. 



With this apparatus, then, Mr. White's experiments were 

 made, and every facility was afforded him by the servants 

 of the establishment. When his experiments were con- 

 cluded, 1 made an analysis of the gas produced, the results 

 of which it is the object of this paper to lay before you. 



