on the terrestrial Rays that occasion Heat. 455 



This glass stops 849 rays of heat, and 949 of light. This 

 accounts for its great use as a darkening glass for telescopes. 



oflth Experiment. 



Sun, Bluish-green glass. 



o' 69i 6 9 ± 



5 7 6 i 71 .. .7: if = ,232 



It stops 768 rays of heat, and j6g of light. 



38th Experiment. 



Sun. Pale-blue glass. 



o' 7°i 7°i 



5 7<?i 7i£...6:if=,i88 



The pale blue glass stops not less than 812 rays of heat, and 

 only 684 of light. 



$Qtb Experiment. 



Sun. Dark-blue glass. 



o' 71 71 



5 m 74i • • • Si : Si = ^38 



The dark-blue glass stops only 362 rays of heat, and 801 of 

 light. 



40^ Experiment. 



Sun. Indigo glass. 



5 672. 64...^: ^=,367 



This glass stops 633 rays of heat, and gggy 3 out of ten thou- 

 sand, rays of light. 



3 N 2 



