47° Dr. Herschel's Experiments on the solar, and 



Qist Experiment, 



Candle. Linen. 



It sJ:ops 690 scattered rays of flame-heat. 



92 d Experiment, 



Candle. White persian. 



o' 57t 57 



5 6oi 58I . . . 3f : if = ,407 



It stops 593 scattered rays of flame-heat. 



93^ Experiment. 



Candle. Black muslin. 



°' 57i 57i 



5 6°i 59 • • • sf : H = >4>35 



It stops 565 scattered rays of flame-heat. 



Transmission of the solar Heat which is of an equal Refrangibility 

 with red prismatic Rays. 



The apparatus which I have used for transmitting prismatic 

 rays, is of the same construction as that which has already been 

 described under the head of direct solar transmissions ; * but 

 here the holes in the top of the box are only two inches from 

 each other, and no more than f ths in diameter.-f On the face of 

 the box are drawn two parallel lines, also f ths of an inch distant 

 from each other, and inclosing the transmitting holes : they 

 serve as a direction whereby to keep any required colour to fall 

 equally on both holes. The distance at which the box is to be 



* See Plate XXI. f See Plate XXII. Fig. 3. 



