318 /- LeConte on the Injluence of Solar Light on Combustion. 



conclusions. The subjoined table will exhibit his results in a 

 convenient form for future reference. 



JExpt. 1. — Green "Wax Taper lost in 5 minutes 



In Dark, Temp. 61'^ I In Sunshine, Temp, 78® Ratio. 



9*25 grg. I 8*5 grs. 



1 : 1-088 



Expt, 2. — Taper Lost, by Burning 7 minutes, in 



Dark, Temp. 67^ 



11 grs. 



Sunshine, Temp. 78^ I Ratio. 



10 grs. j 1 : 1100 



Expt 3. — Mould Candle, to consume 1 inch took, in , 

 Dark, Temp. 68° I Sunshine. Temp. 80° I Ratio. 



56« 0« J 59'« O'^ I ^ • ^'^^^ 



Expt 4. — Taper, to consume 1 inch took, in 



Dark, Temp. 67^ Sunshine, Temp. 79° I Ratio. 



4^^ 30* d'" 0' I 1:1-111' 



EzpL 6. — Taper in Sunshine lost in 10 minutes 



In Painted Lantern. I In Uncoated Lantern, j Ratio. 



16-5 grs. I I5gr8. ) 1:M00 



i 



A sixth experiment, of a similar character, made in a strong 

 moonlight indicated no such diminution in the rate of con- 

 sumption. 



The conclusion to which Dr. M'Keever came was, that solar 

 light does exercise a positive retarding influence on the process of 

 combustion. He supposes this effect to be owing to the well- 

 known influence of the solar rays on many chemical processes: 

 — in some instances accelerating them, but in others retardmg 

 them. Under this point of view, the chemical ra?js may be sup- 

 posed to exercise a deoxydizing power, which, to some extent, 

 interferes with the rapid oxydation of the combustible matter. 

 In confirmation of this opinion. Dr. M'Keever made an experi- 

 ment which appears to indicate that a taper burns more rapidly 

 in the red than in the violet extremity of the solar spectrum. 



In attempting a repetition of Dr. M'Keever's experimentSj 1 

 found it impossible to secure that freedom from agitation in the 

 atmosphere, during the exposure of the burning body to tbe 

 influence of sunshine in the open air, which such an investigation 

 demanded. This was his method of conducting the first four 

 experiments given in the table. The powerful influence exer- 

 cised by comparatively slight disturbances in the air, on the 

 rapidity of combustion, renders attention to this circumstance ot 

 controlling importance. His method of obviating this difficulty 

 by the use of knterns, (as indicated in Experiment 5,) is objec- 

 tionable, from the impossibility of securing precisely identical 

 conditions in relation to the supply of air in the interior. There 

 were, likewise, other considerations which urged me to modily 

 his method of conducting the investigation. It occurred to me, 



