CONSTRUCTION OF RETORTS. 85 



" By this routine the gas and vapours of the earlier hours of the charge will combine 

 and mix with those produced from the later hours, whereby much more and better gas 

 is produced than by any process now adopted, whilst the quantity of coal-tar and of am- 

 moniacal liquor usually formed are both much reduced. 



" If it should be desirable to make gas from coal-tar with these retorts, I introduce an 

 iron pan containing tar into the mouth-piece of each retort at the time of its charging 

 with coal ; and it is only necessary further to observe, that if the charge be a six-hours' 

 charge, the alternations will be every three hours, and so on." 



This arrangement is unattended with the danger that might arise from neg- 

 lected valves on the first-described plan, there being only one hydraulic seal 

 instead of three slide-valves. The loss of gas, from having to open the retort 

 to draw and recharge one half whilst the other half is at work, will be trifling ; 

 for the whole operation does not occupy a minute, and the coal at that period 

 of its distillation and in that time will not produce more than four cubic feet 

 of gas, which will be the full extent of loss. 



The practical benefits that will arise from the adoption of this plan can only 

 be ascertained from experience ; but, judging from the talents and chemical 

 knowledge of the inventor, I expect the results to be favourable. 



PLATE VI. 



REVOLVING WEB RETORT. 



This retort is arranged so that the coal is acted upon in a thin stratum and 

 converted into gas at once : the chemical advantages of this method are 

 many ; all the elements of the coal are liberated at nearly the same time, 

 and unite with one another in such proportions as to form gas of the best 

 illuminating quality, and in greater abundance than when the coal is car- 

 bonized in mass. The condensed bituminous vapour which forms tar in the 

 ordinary process is by this nearly all converted into olefiant gas. 



Fig. 1 . is a longitudinal section through A B in Fig. 3. 



Fig. 2. is a transverse section through CD in Fig. 1. 



Fig. 3. shows end views, with the drum and stand-pipes. 



Fig. 4. plans of the retort in section, over the top of the retort, the web 

 and furnace, respectively. 



Fig. 5. is an enlarged view of the drum. 



The same letters refer to corresponding parts in all the Figures. 



E is a hopper containing the coal ; F is the discharging-disc ; G is the 



