of Oil Gas over Coal Gas. 247 



himself, do not smile to think how he has been cheated in his nu- 

 merals, I shall indeed be surprised. His own calculations will he 

 quite sufficient to show how erroneous must have been his data. 



After tracing the outline of each apparatus, he says, " These 

 are the processes required for producing the oil and coal gas ; 

 but we shall better understand the trouble attendant on the lat- 

 ter, bv a comparative view of two establishments, for a thousand 

 lights each, one for oil, the other for coal gas. Each light con- 

 suming annually upon an average 2000 cube feet of oil gas, and 

 7000 cube feet of coal eas, the whole annual consumption of 

 the one would be 2,000,000, of the other 7,000,000 cube feet." 

 *' The average quantity of oil gas required would be during the 

 fortnight before and after Christmas, somewhat above 16,000 

 cube feet per night, and 56,000 of coal gas." That is, if every 

 burner of the 1000 coal gas lights consumed five cubic feet per 

 hour (which is found to be above the average for the town of 

 Derby), the inhabitants would be required to keep them burn- 

 ing each night eleven hours! i. e. from four in the afternoon till 

 three o'clock next morning 1 ! an event just as probable as the 

 calculation upon which it is founded, or as the truth of the stated 

 number of retorts presumed requisite to furnish such a supply 

 of gas. " To produce that quantity of oil gas, eight or ten retorts 

 would be sufficient, each retort six feet long and six inches dia- 

 meter." — " In the coal-gas work forty retorts at least would be 

 required *, each retort six feet long and one foot in diameter. 

 The utmost quantity of gas which one retort could produce would 

 be 1680 cube feet, working night and day without intermission." 

 — ''Forty retorts required to supply 1000 lifr/ils! ! ! !" Six 

 retorts is the calculation of Mr.Wigston at the Derby Gas-works, 

 for the like number of lights; and from the experience of the three 

 last months' work he finds they will be amply sufficient. His 

 retorts are semi-elliptical, six feet long and two feet diameter, 

 being constructed on the very best principles of exposing a thin 

 stratum of coal to a large surface of heat, and working at short 

 charges. 



Surely Mr. Ricardo must imagine that no improvements have 

 taken place in the manufacturing of coal gas for the last five 

 years; whilst in that of the oil gas it should seem one gallon of 

 oil which formerly made 80 cubic feet of gas will now aflbid 100. 

 But even on the London system of setting up retorts, five in one 



• For the truth of this statement Mr. R. makes a marginal reference to 

 " See Pecltston on Gas Lighti." Novr, in justice to Mr. I'eckston, it is but 

 fair tostfitc, tha' he gives that number as being the cjurintity then (in IHIH) 

 required by the London Companies ; for, in his estimate last yt'nr, to supply 

 1000 lights in Derby, he states ten elliptical retorts as being amply suili- 

 cicnt. 



