on the terrestrial Rays that occasion Heat. 489 



16 ^th Experiment., 



Invisible rays. Violet glass. 



o' 53t 52 



5 ' 54* 53i • • • 1 : i = ^750 



It stops 250 invisible rays of heat. 



165^ Experiment. 



Invisible rays. Crown glass ; one side rubbed on emery, 



rough side exposed. 



o' 49i 4«i 



5 5oJ 49i • • • \i ' f = >4°° 



This glass, so prepared, stops 600 scattered invisible rays of 

 heat. 



166th Experiment. 



Invisible rays. Coach glass ; one side rubbed on emery, 



rough side exposed. 



°' 54 SSi 



5 55i 54 • • • H : i = >50O 



It stops 500 scattered invisible rays of heat. 



i6ytb Experiment. 



Invisible rays. Crown glass ; both sides rubbed on emery. 



o' 50 49i 



5 5H 49f ...if :^ = ,400 



It stops 600 scattered invisible rays of heat. 



168th Experiment. 



Invisible rays. Coach glass ; both sides rubbed on emery. 



°' 54i 54i 



It stops 714 scattered invisible rays of heat. 



