On Halos. 2Zl 



rays which fall upon the fnow being ftoppedj 

 whilfl: thofe which fall on the water are refrafted 

 into their refpeclive colours. Newton accounts 

 for the appearance, by fuppofing that rays of lights 

 in pairing through globules of water, are fome- 

 times in a difpofition to be refledled, and fome- 

 times to be refracted. All thefe fuppofitions how-* 

 ever feem to be unfatisfadory, as the rays will not 

 fall upon the eye in fufficiently itrong pencils. 



The order of the colours in thefe crowns, as 

 laid down by Des Cartes and Huygens, is con- 

 trary to that which Sir Ifaac Newton gives. 



If they judged from fuch as are commonly feen 

 round the moon, they might eafily be deceived, 

 as the colours are in general not very diftinft : 

 the halos I have obferved have uniformly been 

 fimilar to thofe dcfcribed by Newton, at the end 

 of his fecond book of optits. 



Cambridge, Nov. 30, 1786. Three very brilli- 

 ant halos appeared round the moon : the order 

 of the colours, beginning from the moon, was, 

 white of confiderable breadth, yellow, orange, 

 red ; violet, green, yellowifh, red j violet, 

 green, yellowifh, red. The red of a fourth 

 was fo faint as to be fcarcely vifible. The radii 

 of thefe rings might be about one, two, and 

 three degrees, but they were not meafured. The 

 red and violet in each cafe feemed contiguous. 



Dec. ad. A fingle halo appeared round the 



moon •, its diameter was about at , and the 



X colours 



