on the terrestrial Rays that occasion Heat. 457 



These glasses, with the intermediate air, stop 54,2 rays of 

 heat, and 204 of light. 



45^/j Experiment. 



I filled the tube with well-water, and placed it on the trans- 

 mitting apparatus. 



Sun. Well-water. 



o' 52i 5H 



5 5H 55 • • • 6| = sf = ,442 



Here two glasses, with water between them, stopped 558 

 rays of heat. The same glasses, and water, stop only 21 1 rays 

 of light. If we were to deduct the effect of the empty machine, 

 there would remain, for the water to stop, only 16 rays of heat, 

 and 7 of light; but it cannot be safe to make this conclusion, as 

 we are not sufficiently acquainted with the action of surfaces 

 between the different mediums on the rays of heat and light ; 

 I shall therefore only notice the effect of the compound. 



4@tb Experiment. 



I filled now the tube with sea-water, taken from the head of 

 the pier at Ramsgate, at high tide. 



Sun. Sea-water. 



54t 54i 



60 56 5i. : *l:=# l8 



The compound stops 682 rays of heat, and 288 of light. 



47^/6 Experiment. 



Sun. Spirit of wine. 



5 57i 54 • • .'6£: : # == ,388 



The compound stops 612 rays of heat, and 224 of light. 



