240 Mr. Delaval on the Cdufe of the 



in the atmofphere, when in its raref!: flate. Faf 

 the refleflive particles, of the rareft fky, exhibit a 

 blue colour, when viewed by incident light; but 

 the refledive particles of the Tea a6t upon a greater 

 portion of the more refrangible rays ; whereby they 

 exhibit a green colour; and, (as Dr. Ilalley found 

 from adual obfervation) tranfmit a rofe colour, 

 which is red, inclining to violet, at fuch depths as 

 only the lefs refrangible rays can penetrate.* 



Sir Ifaac Newton oblerves that thofe parts of 

 thin plates of water, or air, which by tranfmitted 

 light appear of a colour compounded of red and 



* Newton. Opt. L. I. Part. II. Prop. X. Probl. V. 

 ** Of this kind, is an experiment lately related to me hy 

 " Mr. Halley, who in diving deep into the fea in a diving 

 *' veffel, found in a clear fun fliine day, that when he was 

 '• funk many fathoms deep into the water, the upper part 

 " of his hand, on which the fun ihone direclly through the 

 ** water, and through a fmall glafs window in the veffel, 

 *' appeared of a red colour, like a damafk rofe, and the 

 *' water below, and the under part of his hand, illuminated 

 *' by light reflefted (*) from the water below looked 

 •' green." (*) All the green light, by which the under 

 part of the hand was illuminated, was not refleded from 

 the medium, which was beneath the veffel : for, a part of 

 it was refletled from the ground, over which the veffel was 

 placed. The light, thus refleded from the ground, was 

 tinged green, by paffmg through the fmall depth of water, 

 which intervened between the ground, and the vacant fpace 

 in the veffel, under the hand : whereby the rays, reflefted, 

 from the ground, were mi.xed with the green rays refieded 

 from the internal parts of the fea water. 



violetj 



