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LXII. Intelligence and Miscellaneous Articles. 



THE RADIANT ENEEGY OF THE STANDARD CANDLE ; MASS OF 

 METEOES. BY C. C. HUTCHINS. 



nPHE following investigation was undertaken with the primary 

 ■*- object of finding, if possible, more trustworthy data for deter- 

 mining the mass of shooting-stars ; but a reliable determination of 

 the radiation of the standard candle cannot fail to be of value for 

 other purposes. 



The apparatus employed in making the measurements was my 

 thermograph*, the constant of which was found in the two follow- 

 ing ways. 



First metliod. — A copper Leslie cube, holding about 3 kilog. of 

 water, was placed behind an opening of 16 square centim. in a 

 wooden screen, which opening was closed by a movable shutter, by 

 opening which the thermograph, one metre distant, could be 

 exposed to the radiation from the cube. 



The following quantities were then determined : — dimensions of 

 cube; weight of water contained in cube; water-equivalent of cube ; 

 mean of the galvanometer-deflexions taken during the interval that 

 the cube and its contents were falling 5° from a temperature about 

 65° above that of the air ; time in seconds occupied by the cube in 

 falling the 5° as above. 



Knowing these quantities, we can evidently compute in ergs per 

 second the radiant energy passing through the square centimetre 

 of surface containing the thermal junction, and such that it will 

 produce a deflexion of one division of the galvanometer-scale. A 

 number of trials showed that 16*9 ergs per second was the quantity 

 required. 



Second method. — The constant was found by passing the rays of 

 the sun through openings of 0*394 and 0*23 centim. diameter, and 

 observing the galvanometer-deflexions when the thermograph was 

 exposed in the divergent beam at a point where the diameter of the 

 beam was 4*2 centim., and then computing the deflexion for the 

 undiminished sunlight. Simultaneously with the above measures 

 the radiation of the sun was observed with Pouillet's pyrheliometer. 



The mean of several sets of measures by this method gave the 

 constant 17*02; agreeing better than could have been expected 

 with the results of the first method. The candle employed was 

 the ordinary sperm candle, six to the pound. It burned in still 

 air, without snuffing, 7*37 grm. per hour. The radiation of the 

 candle was measured by placing it behind the screen in place of the 

 cube employed in finding the instrumental constant, the exposures 

 being made in the same manner as for the cube. The deflexion 

 given varied very much with the length of the wick of the candle, 

 constantly increasing for a half hour or more after lighting. It 

 therefore was necessary to observe the deflexion at what was con- 



* Proc. American Academy, 1889. 



