462 Dr. Herschel's Experiments on the solar, and 



6oth Experiment. 



Sun. Linen. 



o' 63 63 



5 ^9 6 3i • • • 6 ' i — ^833 



White linen stops 916 scattered rays of heat, and 952 of 

 light. 



615/ Experiment. 



Sun. White persian. 



6' 70 70 



5 7^i 71^. ..6^: i| = 5 240 



This thin silk stops 760 scattered rays of heat, and 916 of 

 light. 



6id Experiment. 



Sun. Black muslin. 



70 6<J£ . . . 5k • H = ,286 



This substance stops 714 scattered rays of heat, and 737 of 

 light. 



Transmission of terrestrial Flame-beat through various Substances. 



My apparatus ^for the purpose of transmitting flame-heat is 

 as follows.* A box 22 inches long, 5^ broad, and 1^ deep, has 

 a hole in the centre i~ inch in diameter, through which a wax 

 candle, thick enough entirely to fill it, is to be put at the bot- 

 tom ; the box being properly elevated for the purpose. There 

 must be two lateral holes in the bottom, 2 inches long, and ji 

 broad, one on each side of the candle, to supply it with a cur- 

 rent of air, as otherwise it will not give a steady flame, which 

 is absolutely necessary. At the distance of 1 j% inch from the 

 candle, on each side, are two screens, 12 inches square, with 



* See Plate XXIII. Fig i. 



