1 8 Experiments on the Solar, and on the 



give a comparative view of the operations that may be per- 

 formed on the rays that occafion heat, and of thofe which 

 we already know to have been effected on the rays that oc- 

 cafion light, it will be neceflary to take a fhort review of the 

 latter. I {hall merely felect fueh facts as not only are per- 

 fectly well known, but efpeciallv fuch as will anfwer the in- 

 tention of my comparative view, and arrange them in the 

 following order. 



i. Light, both folar and terre final, is a fenfation occa- 

 iioned by rays emanating from luminous bodies, which have 

 a power of illuminating objects ; and, according to circum- 

 flances, of making them appear of various colours. 



2. Thefe ravs are fubject to the laws of reflection. 



3. They are likewife fubject to the laws of refraction. 



4. They are of different refrangibflity. 



5. They arc liable to be flopped, in certain proportions, 

 when tranfmitted through diaphanous bodies. 



6. They are liable to be fcattered on rough furfaces. 



7. They have hitherto been fuppofed to have a power of 

 heating bodies j but this remains to be examined. 



The fimilar proportions relating to heat, which are in* 

 tended to be proved in this paper, will Hand as follows : 



1. Heat, both folar and terreflrial, is a fenfation occa« 

 fioned by rays emanating from candent fubftances, which 

 have a power of heating bodies. 



2. Thefe rays are fubject to the laws of reflection. 



3. Thev are likewife fubject to the laws of refraction. 



4. Thev are of different refrangibility. 



5. They are liable ^to be flopped, in certain proportions^ 

 when tranfmitted through diaphanous bodies. 



6. They are liable to be fcattered on rough furfaces. 



7. They may be fuppofed, when in a certain flate of 

 energv, .to have a power of illuminating objects; but this 

 remains to be examined. 



Before I can go on, I have to mention that the number 

 of experiments which will be required to make good all thefe 

 points, exceeds the ufual length of my papers; on which 

 account, I fhail divide the prefent one into two parts. Pro- 

 ceeding, therefore, now to an iuvefligatkm of the three firfl 

 9 heads 



