338 AZIMUTH AL CHANGES OF HILLS, 



so severely tested, that it has now obtained universal acceptance. 

 It is, perhaps, needless to remind you that it supposes light to be 

 propagated from a luminous body, which excites a series of suc- 

 cessive undulations in a highly elastic a3therial medium. Such a 

 medium must then exist otherwise the light of the sun could 

 not be transmitted to us if, as we infer, undulations are the 

 mode of doing so. 



Then we may fairly conclude that there is an a3therial medium 

 pervading all space, dense indeed in the vicinity of substantial 

 bodies, but dwindling away in space into extreme rarity. 

 There is then no obstacle to Encke's theory, which unites great 

 simplicity with all reasonable probability. And we cannot avoid 

 being struck with the beautiful manner in which it assists the 

 Undulatory Theory of Light ; the one helps to establish the 

 theory of the other, and we are forcibly reminded of the truth of 

 Bacon's observation, that " no natural phenomenon can be 

 adequately studied in itself alone, but to be understood ; it must 

 be considered as it stands connected with all nature." 



On certain possible relations between Geological Changes and 

 Astronomical Observations. 



By G. R. SMALLEY, ESQ. 



[Eead October llth, 1865.] 



IT is, I confess, somewhat doubtful, whether the title of the 

 present paper sufficiently expresses the purport of my remarks 

 this evening. It has been selected for want of a better ; but the 

 real object that I have in view is to show that certain localities 

 may be undergoing some slow geological changes of a most 

 singular and unexpected character, changes imperceptible to 

 any ordinary observations, but capable of detection by delicate 



