Qg6 Dr. Herschel's Experiments on the Solar, and 



5. They are liable to be stopped, in certain proportions, when 

 transmitted through diaphanous bodies. 



6. They are liable to be scattered on rough surfaces. 



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

 heating bodies ; but this remains to be examined. 



The similar propositions relating to heat, which are intended 

 to be proved in this paper, will stand as follows. 



1. Heat, both solar and terrestrial, is a sensation occasioned 

 by rays emanating from candent substances, which have a 

 power of heating bodies. 



2. These rays are subject to the laws of reflection. 



3. They are likewise subject to the laws of refraction. 



4. They are of different refrangibility. 



5. They are liable to be stopped, in certain proportions, when 

 transmitted through diaphanous bodies. 



6. They are liable to be scattered on rough surfaces. 



7. They may be supposed, when in a certain state of energy, 

 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 malfe good all these 

 points, exceeds the usual length of my papers; tin which account, 

 I shall divide the present one into two parts. Proceeding there- 

 fore now to an investigation of the three first heads that have 

 been proposed, I reserve the three next, and a discussion which 

 will be brought on by the seventh article, for the second part. 



1st. Experiment. Reflection of the Heat of the Sun. 



I exposed the thermometer which in a former paper has been 

 denoted by No. 3, to the eye-end of a ten-feet Newtonian 



