33^ On Halos. 



I have added this laft feriesj x—x+x—x. Sec. 

 becaufe it has lately been the fubjed of much 

 debate, and I have determined its fum by a dif- 

 ferent method to others. Mr. Vince is right in 



calling^the fum of this feries -^, though the me- 

 thod by which he made his deduftion was falfe, 

 and which gave his opponents the opportunity 

 of faying, that the fum of the feries might have 



been-—, —- or — -r — as well as — 



3* 4 anything •'"^*»'*'' 2. 



On Halos, by the Rev, James Wood, A. M. 

 Fellow of Si. John's College^ Cambridge. Commu- 

 nicated by 'Thomas Percivaly M.D. F.R.S. 6f^. 



READ OCTOBER 12, I787. 



DIFFERENT hypothefes have been made 

 ufe of by Des Cartes, Huygens and New- 

 ton, to account for the appearance of Halos, or 

 coloured circles, round the fun and moon. The 

 firll of thefe fuppofes rays of light to be refradled 

 by pieces of ice formed like double convex 

 lenfes, which however, he confefles, we never 

 find upon the furface of the earth. Huygens 

 fays that halos are caufed by fmall globules of 

 fnow, furrounded each by a fhell of water ; the 



rays 



