80 



CONTRIBUTIONS TO THE KNOWLEDGE 



of a bench containing two resin-gas retorts and two water- 

 gas retorts of the largest size. The water retorts discharged 

 themselves into the resin retorts, and these last worked into 

 a hydraulic main, from which the gas passed successively 

 through a refrigerator and wet lime purifier to the gas holder, 

 a vessel of the ordinary construction, and capable of contain- 

 ing about 18,000 cubic feet. 



The volume of gas produced was measured by a meter placed 

 between the last purifier and the holder; a copper for melting 

 the resin, and an oil cistern for collecting the residual oil 

 condensed in the hydraulic main and refrigerator during the 

 process, completed the apparatus. 



Before commencing each experiment, the quantity of gas 

 in the holder was carefully determined, and a specimen with- 

 drawn for analysis ; the charcoal retorts were then filled, the 

 resin melted in the oil of a former working — about 7^ gallons 

 being used for each 1 l^lbs. of resin, — and the water and oil 

 tanks being first accurately gauged, the process of gas-making 

 was commenced by admitting properly regulated streams of 

 resin and water into their respective retorts. 



The temperature of the gas, as it passed through the 

 meter, was found never to exceed 60°F., and was frequently 

 much below this point, thus affording a sufficient guarantee 

 for the correctness of the numbers read ofi". 



The specimens of gas were drawn from the holder on the 

 morning following each experiment, in order to insure perfect 

 mixture and a fair sample ; and the analyses of these gasea, 

 as well as those examined in the experiments upon coals and 

 cannels, were made over mercury, according to methods which 

 I have fully detailed in the Journal of the Chemical Society, 

 (vol. ii. p. 269, June, 1849,) with this difference, that a new 

 form of apparatus was employed, which will be elsewhere 

 described. This instrument much shortens the processes, 

 without rendering them less accurate. The volume of the 

 gases was always read oflF when they were saturated with 



