392 On Light. 



be difficult to explain why every pencil of rays is not in 

 some degree particoloured ; at leaist momentarily. I 

 should, therefore, incline to the opinion, that the rays, 

 which produce the diiferent impressions of colour, dif- 

 fer in their weight. 



If I mistake not, the facts, which I have mentioned 

 above, all lend their influence, with some diversity in- 

 deed, to the support of these positions. 



I am, Sir, yours, Sec. 



T. DWIGHT. 



