176 ANNUAL OF SCIENTIFIC DISCOVERY. 



ness of its colors, yet, in another respect in the comparatively small 

 amount of heat which accompanies its rays in proportion to the light 

 itself it is greatly superior to every sort of artificial light. The 

 great amount of heat in our artificial lights is absolutely useless. It 

 is nearly all intercepted by the humors of the eye. 



DISCOVERY IN PHOTOMETRY. 



It is the established practice in measuring the light of illuminating 

 gas to compare the light of a five feet Argand burner with that of a 

 spermaceti candle burning 120 grains an hour ; and when the candle 

 used burns less or more than the 120 grains it has been regarded as a 



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matter of course that the light would vary in the same proportion. But 

 scientific evidence recentlv given before the committee of the House 



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of Lords, in England, on the bill of the Birmingham Gas Company, 

 respecting the illuminating power of the gas supplied by the two ex- 

 isting companies in that town, has shown that a candle burning a large 

 quantity of spermaceti, yields more light in proportion to the material 

 consumed than a candle burning a small quantity. The Journal of 

 Gas Lighting (London), after giving a full history of the case, 

 remarks : 



"These experiments demonstrate that the illuminating power of 

 'burning candles increases in a greater ratio than the direct propor- 

 tion of the consumption of spermaceti. It has long been known that 

 the illuminating power of gas increases in a greater proportion than 

 the quantity consumed, but we believe it had not been previously 

 known that the same law operates in the combustion of candles. It 

 is evident, from the results of the photometrical experiments with the 

 gas supplied by the Birmingham companies, that no correct conclu- 

 sions can be drawn from proportionate quantities of either the gas or 

 spermaceti consumed, inasmuch as the amount of light is iniluenced 

 by the quantity of combustible matter burned within a given time. 

 It has been suggested that some rule may be established by which the 

 influence on the light of the flame, produced by the relative quantities 

 of spermaceti undergoing combustion, maybe determined and allowed 

 for. Thus, it is probable that after the proportions have been 

 reduced to 120 grains consumed per hour if one per cent for each 

 grain of spermaceti the candle may consume per hour less than 120 

 grains, be deducted from the indications of the photometer, and if one. 

 per cent be added to similar indications of the photometer for each 

 grain the candle may consume more than 120 grains, the results 

 attained would not be far from the truth. But until the subject has 

 been further investigated it would not be safe to assume positively 

 that such a scale of compensation would be correct. The new light 

 which these experiments have thrown on photometry, shows the neces- 

 sity for the adoption of some more certain standard of comparison 

 than a spermaceti candle, the consumption of which it is impossible 

 to regulate with accuracy. The Carcel lamp which is similar to the 

 ' moderator ' lamp is adopted generally on the Continent as the 

 standard of comparison, and it possesses these advantages, the con- 

 sumption of oil may be regulated with the greatest nicety, while its 

 flame approaches in luminosity that of nine candles. At the same 

 time, it must be observed that the lamp-wick requires great attention, 



