152 ANNUAL OF SCIENTIFIC DISCOVERT. 



less from a conviction that some error must have occurred either 

 in the metliod or record of observation. Nevertheless, Dr. Mc- 

 Keever's expei'iments appear as additions in the Cavendish Soci- 

 ety's translation of the Ilandbook. The summary of his results 

 may be stated thus : It required eleven minutes to burn in the 

 sunshine the same weight of candle that burned in the dark in ten 

 minutes. 



Similar experiments were made at a later period by Dr. Morvill 

 Wyman of Cambridge, and reported to the American Academy 

 of Arts and Sciences. Ths result at which he aiTived was exactly 

 the reverse of that reached by Dr. McKeever. He burned two 

 sperm candles, each alternately for half an hour in the sunshine 

 and darkness, and found the candle, during its exposure to sun- 

 shine, burned more rapidly than when in the dark. 



In 1856, the subject was taken up by Prof. Joseph Le Conte of 

 Columbia, S. C. He concentrated, witli the aid of a rellector and 

 burning glass, the sun's rays upon the ilame only of a wax 

 (sperm) candle in a large, dark room. At the same time another 

 candle was burning in the same room, under identical circum- 

 stances, except that tiie flame was not exposed to the sun's rays. 

 The result showed that tlie effect of the sun's rays, thougli greatly 

 exaggerated by concentration, when confined to the flame, did 

 not appreciably increase the consumption of tallow. 



Here, then, we have, apparently, all possible results of experi- 

 ment, to wit: Sunshine diminishing the rate of combustion, as 

 observed by Dr. McKeever ; augmenting the rate, as observed l)y 

 Dr. Wyman, and producing upon it no effect whatever, as shown 

 by Prof. Le Conte. 



Dr. McKeever ascribed the retai'dation to some peculiar effect, 

 as of interference,of the solar rays upon flame. 



Dr. AVyman infeiTcd that the sunsliine, by warming the tallow 

 of the candle exposed to it, facilitated its melting, and by so much 

 spared, for destructive distillation and combustion, the heat of the 

 flame, which would have otherwise, in larger measure, gone to 

 liquefy the tallow. 



Le Conte conclusively showed that, when the column of wax or 

 tallow is sheltered, and the sunshine directed solely on the flame, 

 the effect on the consumption of the tallow is too small to be 

 recognized. 



The observations of the latter experimenters agree in throwing 

 doubt ujion the inferpretation Dr. McKeever gives of his own 

 experiments. 



Prof. Horsford ascribes the source of error in Dr. McKeever's 

 investigation to the incidental greater flaring of the candle in the 

 dark. The experiments with the lantern he explained by the 

 well-known effect of dark paint in absorijing radiant heat, and 

 converting it into heat of conduction, by which the air in the 

 painted-glass lantern was more heated than in the lantern not 

 painted. 



Prof. Horsford then gave an account of the diminished draft in' 

 the range flue of his dwelling-house during the recent hot terra, 

 which rendered it impossible to bake meats or bread in the oven 



