4S4 THE POPULAR SCIENCE MONTHLY. 



been considering, did not deem it practicable to change at once to the 

 use of pure petroleum or naphtha gas in Boston, as the burners in use 

 are, for reasons already given, not suitable ; the works employed to 

 produce coal-gas are not adapted to this, and as the flame of petro- 

 leum-gas " burning in an appropriate burner is a very small flame," it 

 would not in their opinion prove satisfactory to consumers, although 

 the amount of light would be the same if not greater. The objection 

 that petroleum-gas in any form injures the metres was found to be 

 without warrant. 



The practice which obtains with the Detroit Mutual Company and 

 others, of adding air to naphtha-gas to reduce its illuminating power 

 so that it can be burned in an ordinary burner, was judged by the com- 

 missioners to be the reverse of economical, to both the company and 

 consumer, because the deterioration of the gas by this means is in 

 greater ratio than the increase of its volume. It is said that one per 

 cent, of air will reduce the illuminating power six per cent., or more 

 than carbonic acid, the removal of which is considered necessary 

 by all gas-engineers for the sake of economy. It was for this reason 

 that the first attempt to make illuminating gas from petroleum (that 

 at Saratoga by the Gale and Rand process) failed. 



What is true of the value of naphtha as a gas-making material used 

 alone, is also true of its value as an enricher. Experiments already 

 here referred to, although not expressed in terms of equality, imply 

 the superiority of naphtha to Albertite, which is about the best 

 of the enriching coals. The yield from a ton of the latter, which costs 

 about $25, was, on the average of a number of experiments made by 

 the Boston Gaslight Company, only 14,694.4 cubic feet of 55 candle 

 gas; while the yield of $25 worth of naphtha (valuing it at ten 

 cents a gallon, which is rather high) would be 19,872.5 cubic feet 

 of 64.5 candle gas, or 5,178.1 cubic feet more gas of richer quality 

 than a ton of Albertite. By the use of naphtha, too, a larger amount 

 of gas is obtained from the ordinary caking coal. In enriching with 

 Albertite the coal with which it is mixed is distilled in an iron retort 

 at a comparatively low temperature; while, if naphtha be used, all of 

 the common coal can be carbonized in a clay retort, which is acknowl- 

 edged by all to be more economical, and all of the gas in the coal 

 can be exhausted, so that about 1,000 cubic feet more can be obtained 

 per ton. The iron retorts are more expensive than the clay, because 

 their first cost is greater, and they do not last as long. In making 

 gas on a large scale, about one-half the number of retorts can be dis- 

 pensed with, in the use of naphtha as an enricher. The New York 

 Mutual Gas Company, for example, in this way, make as much gas 

 with forty retorts as can be made in the other with eighty ; and with 

 the disuse of the extra forty retorts the labor necessary to tend them is 

 dispensed with. The increased yield of the coal by the use of naphtha, 

 referred to just now, is demonstrated by practical experience to be 



