ACCOUNT OF ANTHELIA, 



OBSERVED m ASCENDING SNOWDON, on the 17 th of May. 1826. 



BY JOHN BLACKWALL, F. L. S. 



(Read October 5tb. 1827.) 



Notwithstanding the production of an- 



thelia and halos has engaged the attention of 

 many eminent philosophers, it is pretty generally 

 admitted, that no satisfactory theory of these 

 singular phenomena has hitherto been promul- 

 gated. The most prevalent opinion, relative to 

 their formation, appears to be, that they are 

 occasioned by the refraction and reflection of 

 light, by minute particles of ice floating in the 

 atmosphere ; but, although Descartes, Huygens, 

 Newton, Marriotte, Young, and other distin- 

 guished individuals have either supported this 

 doctrine by their writings, or have sanctioned it 

 by their approval, the facts I am about to relate 

 plainly demonstrate, that water, in a state of 



