216 THE KEFKACTION OF SOUND. 



counteracted by the downward refraction from diminution of tempera- 

 ture. This was observed not to be the case when the cloudiness of the 

 night prevented terrestrial radiation and the deposition of dew. — {Proc 

 B. S., 1876.) 



It has thus been shown in the course of this discussion, that while 

 the refraction of sound as illustrated by gas lenses, still retains its 

 original interest as a striking class-experiment, the far more important 

 examples of acoustic refraction constantly presented by the infinitely 

 varied conditions of differing air-currents and of differing air-tempera- 

 tures, have until very recently, attracted no attention, and their prac- 

 tical significance has been strangely overlooked. 



