82 CONSTRUCTION OF RETORTS. 



in their places : the slides F 1 and F 2 are opened, and C 1 and C 3 closed. The 

 bituminous vapours that rise first will pass through the pipes E E, and thence 

 through the entire length of the hot retorts A 2 and A 4 , and be converted into 

 gas, which will pass to the hydraulic main by the stand-pipes on which the 

 slide-valves C 2 and C 4 are fixed, and which remain open. When the distilla- 

 tion has gone on for half the duration of the charge viz. three hours the 

 valves C 1 and C 3 are opened, F 1 F 2 shut, and the gas evolved from the retorts 

 A 1 and A 3 passes through the stand-pipes attached to them. The retorts A 2 

 and A 4 are now charged, the mouths closed, the valves F 1 and F 2 again 

 opened, and C 2 and C 4 shut. The operation is now reversed, the first vapours 

 passing through the two first-charged retorts until their charge is expended, 

 when C 2 and C 4 are opened, F 1 and F 2 closed, and the charge drawn. They 

 are then immediately recharged, and the operation of opening and closing the 

 valves repeated. 



The working doubtless appears complicated, and I must unquestionably 

 acknowledge this method to be so. None of these valves, however, formed 

 any part of Mr. Lowe's original patent ; they are an addition, and certainly 

 not an improvement. Retorts on this construction have been for some months 

 at work at the Pancras station of the Imperial Gas Company, and I believe 

 are found to act well, producing gas of average quality and in greater abun- 

 dance than by the ordinary method. The reason of the gas being only of 

 an average quality is, that the carburetted hydrogen made after the produc- 

 tion of bituminous vapour has ceased, still passes over the red-hot surface of 

 another retort and deposits some portion of its carbon, the rich gas formed 

 by the conversion of the bituminous vapour only serving to make up the 

 deficiency. 



If, instead of having only two retorts in a set, the number could be in- 

 creased to six, and after the first hour the gas be allowed to pass away on 

 the ordinary plan, then, I think, both the quantity would be augmented and 

 the quality improved. 



By Mr. Lowe's own arrangement the complication of valves is done away 

 with, and the chance of deposition of carbon from the after gas is decreased, 

 owing to the reduced length of the retort, and consequently the diminished 

 area of heated surface over which the gas has to pass. The annexed wood- 

 cut (Fig. 20.) exhibits the plan proposed by him in his specification, from 

 which the following extract is taken. 



