a 



518 Dr. Herschei/s Experiments on the solar, and 



to be made that have been planned for execution ; yet, even 

 then, 128 visible and o>9^ invisible rays to be intercepted, will 

 only make up 522'; so that a deficiency of 36 must still remain. 



In sea-water, the balance will stand thus : 288 rays of light 

 give 175 rays of heat; these and 394, invisible rays make up 

 569 ; but the rays actually intercepted were 682, which argues 

 a deficiency of no less than 113 rays. 



But if I have for a moment admitted the entire stoppage of 

 the invisible rays of heat in liquids, the same indulgence can- 

 not be granted for the empty tube, as we know it does neither take 

 place in glasses, nor in air. Therefore we must calculate thus: 

 this compound of glass and air stops 204 rays of light; these 

 can amount only to 124 rays of heat; but it is found to stop 

 542 of them, so that 418 remain to be accounted for. Now, 

 we certainly can not suppose more than 100 of them to owe 

 their 'deficiency to the store of invisible heat; so that 318 will 

 still remain unaccounted for. 



And thus, from the second table, we have given instances 

 where the assumed hypothesis of visible and invisible heat, in 

 certain proportions, would require a greater stoppage than our 

 experiments will admit ; and now, on the contrary, it appears, 

 that interceptions calculated according to the same hypothesis, 

 should be less than the results in the third table give them. 

 From which we conclude, that every other proportion fixed 

 upon, would always be erroneous, either in excess or in defect. 



Equal contradictions may be shewn to attend all endeavours 

 to account for the results contained in our fourth table, by ad- 

 mitting any visible heat at all, let the quantity be what it will. 

 To make the proof of this general, let 1000 be the total heat, 

 and assume x for that part of it which we would suppose to be 



