168 IJAINBOW. [Lesson xxvi. 



will be separated from one another. Hence it 

 may be easily perceived, that some of the falling 

 globules may be in that position which will cause 

 the rays that produce a red colour to fall upor the 

 eye, others next to them below will send forth 

 orange-making rays, the drops next to them will 

 cast the yellow-making rays, and those suc- 

 cessively in order below them, will refract the 

 blue, indico, and violet-making rays to the eye; 

 and thus, in a certain space in the cloud, all the 

 colours will appear ; and since, under the same 

 angles, the same phcenomena will be produced, 

 therefore an arch of this various-coloured light 

 must necessarily be produced in the clouds. 



The different sizes of the Rainbows depend en- 

 tirely upon the height of the sun at the time : for 

 when the sun is in the meridian, or at his highest 

 altitude, the bow will then be least to our sight, 

 being but a small segment of a circle; but as the 

 sun gets lower and lower, the bow will increase in 

 height; and when the sun is in the horizon, or just 

 setting, a bow at that time is as large as it can be, 

 being very nearly semi-circular. It may also be ob- 

 served that at all those places and times when the 

 altitude of the sun is more than 42 no primary 

 Rainbow can appear ; and when his altitude ex- 

 ceeds 54l no secondary bow can appear. 



With regard to the part of the sky in which a 

 Rainbow appears, when I say that it is always 

 opposite to the sun, I present you with an invariable 

 rule where to find it ; and this is anadditional reason 



for 



