CLOUDS AND RIVE11S, ICE AND GLACIERS. 11 



because of its competence to explain all the phenomena 

 of light that the wave theory now receives universal 

 acceptance un the part of scientific men. 



Let me use an illustration. We infer from the 

 flint implements recently found in such profusion all 

 over England and in other countries, that they were 

 produced by men, and also that the Pyramids of Egypt 

 were built by men, because, as far as our experience 

 goes, nothing but men could form such implements or 

 build such Pyramids. In like manner, we infer from 

 the phenomena of light the agency of waves, because, 

 as far as our experience goes, no other agency could 

 produce the phenomena. 



§ 4o The Waves of Heat which produce the Vapour of our 

 Atmosphere and melt our Glaciers. 



29. Thus, in a general way, I have given you the 

 conception and the grounds of the conception, which 

 regards light as the product of wave-motion ; but we 

 must go farther than this, and follow the conception into 

 some of its details. We have all seen the waves of 

 water, and we know they are of different sizes — different 

 in length and different in height. When, therefore, 

 you are told that the atoms of the sun, and of almost 

 all other luminous bodies, vibrate at different rates, and 

 produce waves of different sizes, your experience of 

 water-waves will enable you to form a tolerably clear 

 notion of what is meant. 

 3 



