Lesson xxvi.J RAINBOW. 167 



een in the clouds, as a pledge of inviolable- fidelity 

 and infinite mercy j assuring us, that, " while the 

 "earth remaineth, seed-time and harvest, and 

 " cold and heat, and summer and winter, and day 

 (t and nigh*, shall not cease." How gracious and 

 benevolent that BEING, who so often renews a 

 covenant of kindness and mercy to his creatures; 

 and that too, in such a manner as to raise pleas- 

 ing sensations in every heart, and charm every 

 beholder ! 



To account for the production of the Rainbotv, 

 we are in the first place (o consider, that it is never 

 seen but in the time of rain, or near it, and when 

 the sun shines. You will understand, then, that 

 when a ray from the sun falls upon a drop of rain 

 in a cloud, if it enter the^ upper part of the drop 

 in a proper situation, it will, by refraction, be 

 thrown upon the inner surface of the back part of 

 'the drop; from thence it will be reflected to the 

 lower part of the drop, at which place undergoing 

 a second refraction, it will be bent towards the 

 earth : and thus rays of the sun, after one re- 

 flection, and two refractions, may come to the 

 eye of a spectator, whose back is towards the sun, 

 and his face towards the drop. When rays which 

 are effectual, emerge from the drop after one re- 

 flection and two refractions, those which are most 

 refrangible, will, at their emersion, make angles 

 with the incident rays, different from. those which 

 are least refrangible; by which means the rays 

 that produce the sensations of different colours 



will 



