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the sun fall, and after various refractions and reflections, 

 strike on the eye of the beholder. This is rendered in- 

 disputable from hence, that the very same colours, and 

 in the same order, are exhibited in the drops of water, 

 spouted from a fountain. 



The moon also sometimes exhibits a rainbow : but 

 only when she is full : her light being at other times too 

 faint to affect the sight, after two refractions and 

 a reflection. It has all the colour of the solar rain- 

 bow, very distinct and pleasant, only considerably 

 fainter. 



A rainbow is likewise sometimes exhibited by the sea, 

 when a strong wind carries the tops of the waves aloft, 

 and the sun's rays falling upon them are refracted and 

 reflected, as in a shower. But the colours of this are 

 less lively, less distinct, and less durable than those of 

 the common bow. Scarce above two colours are distin- 

 guishable, a dark yellow on the side next the sun, and a 

 pale green on the opposite side. But sometimes 20 or 

 30 of them are seen at once. They appear at noon-day, 

 in a position opposite to that of the common rainbow, 

 the concave side being turned upwards. 



5. Halo's are circles of various colours, which are 

 sometimes seen about the sun or moon. The space con- 

 tained within them (especially near those parts which are 

 tinctured with the most lively colours) is more dusky 

 than the sky without. (They never appear in rainy 

 weather.) Perhaps the air is at that time full of very 

 small icy particles, on which the rays of the sun and 

 moon falling, after refraction, exhibit that appearance. 



6. As to mock suns, we sometimes see a large, white 

 circle, parallel to the horizon, in several parts whereof 

 more or fewer suns appear, though not always of the 

 same size or colour. As an halo frequently appears at 

 the same time, it is probable they spiing from much the 

 same cause, namely, from icy particles floating in the 



