768 



the quantities of different bodies necessary to give the same amount of light, dis- 

 regarding luminosity: 



Young's paraffin oil . 

 American petroleum, No. 1 

 No. 2 



Paraffin candles . 

 Spermaceti candles . . 

 Wax 



Stearine . . 



Tallow 



4'53 litres. 

 570 

 5-88 



8-42 kilos. 

 10-37 

 11-95 

 12-50 



16-30 



Dr. Macadam ['Royal Scottish Society of Arts,' voL viii. 1871] compared the 

 photogenic power of mineral oil with its animal and vegetable rivals with the follow- 

 ing results : 



In a cottage-lamp, paraffin-oil at 2s. per gallon burned for 9 hours with a luminosity 

 of 6-candle power for a \d., and in a parlour-lamp this oil burned for 6 hours, giving 

 9-candle power for the same price ; while it burned the same money value in the 

 dining-room lamp in 4,J hours giving 12-candle power. 



In setting it against coal-gas, Dr. Macadam assumes the high candle-power given 

 by Scotch gas companies, and he takes a moderate price which is not now likely to 

 prevail. Assuming gas to sell at 5s. per 1,000 cubic feet, and to have a luminosity of 

 28 candles, he finds gas cheaper than paraffin oil, if consumed at No. 3 jet ; but should 

 gas cost 5s. Sd. per 1,000 cubic feet, the two illuminating agents are equal. When 

 this high candle-power of gas is withdrawn they are also equivalent in price and 

 luminosity. Paraffin oil is as cheap as gas when the latter is consumed at No. 3 jet, 

 and its cost is 5s. per 1,000 cubic feet; while its luminosity is 24'70-candle power; 

 or at No. 4 jet when the same-priced gas is of 21 -53-candle' power ; or at No. 5 jet 

 when it is only 20-candle power. 



Silber proposes to burn oils in rooms from permanent pendants, just as we do gas ; 

 and with special contrivances for the purpose has attained very marked results. 

 [' Journal of the Society of Arts,' vol. xix. p. 88.] Using petroleum of sp. gr. 795 ho 

 obtained an illuminating power perhaps 20 per cent, greater than the London 

 coal-gas, which is given to the consumer at from 12 to 15 candles; though with 

 gas at 3s. 9d. per 1,000 cubic feet the cost of petroleum was 10 to 20 per cent- 

 greater than the gas. But by an alteration in the argand the illuminating power was 

 increased from 40 to 60 per cent, more than at first. So though colza lamp costs fivo 

 times as much as the gas ; Valentin's experiments gave with Silber's lamp a light 

 equivalent to a saving of 500 per cent. Mr. Silber is now adapting his lamp to uso 

 the heavier and safer mineral oils. See SILBER LIGHT. 



Use of mineral oils in gas-making. It has been proposed to use mineral oils in gas- 

 making either by naphthali&ing the poor gas made from ordinary coal, or by the con- 

 version of the rich, oily hydrocarbons into permanent gas. 



1. Beautiful results have been obtained by passing the gas through oils, whether of 

 heavier or lighter specific gravity. The objections of smell, and the tendency of oil 

 to return to its original state, have militated against the extensive use of this method 

 in domestic circles. It appears generally necessary that the carburetter be as close as 



