refractive and dispersive Powers of the Atmosphere, fyc. 207 



each other. Viewed as I have seen her from the heights of 

 mountains and in the clearest nights, she appears of a brilliant 

 white light. And the varying colours of her disk seem to be 

 caused by varieties in the colouring power of our atmosphere 

 alone. What I am trying to clear up is, that astronomers, in 

 considering the refractive powers of atmospheric air, have over- 

 looked the circumstance that there is almost no state of the 

 air in which the diffusion more or less of aqueous gases or 

 cloudiness does not exist, though in a very small degree ; and 

 that on this diffusion of cloudiness depends in a greater degree 

 than is imagined, the dispersive power of the atmosphere and 

 the peculiar colours of the celestial bodies seen through it. 



I shall conclude my remarks on the Moon with the de- 

 scription of a curious lunar refraction, which I observed some 

 years ago. About seven o'clock in the evening, the Moon 

 being five days old, I noticed a remarkable double refraction 

 of her image of the following form and relative position D j) , 

 that is, two distinct crescents instead of one, and both so pre- 

 cisely similar as not to be distinguished ; so that I said to a gen- 

 tleman who was with me, " Which do you think is the Moon, 

 and which the paraselene?" Neither of these images was 

 coloured, and both were as bright as the ordinary brightness 

 of the Moon. The cause of this phsenomenon did not suggest 

 itself at the time ; but I have since thought that it so much re- 

 sembled the double refraction by which two images are seen 

 in certain laminated spars, that it might be referrible to the 

 same cause, and that it might be an indication that there ex- 

 isted atmospherical laminae at that time. I do not conceive 

 that the existence of laminated air is by any means improba- 

 ble, and it may be connected possibly with the various con- 

 trary currents of air, which exist contemporaneously in suc- 

 cessive altitudes in the atmosphere, of which observations on 

 the varying direction of small air balloons have furnished me 

 with abundant proof. 



The above subjects deserve more consideration than they 

 have hitherto met with, and I trust many members of the So- 

 ciety will co-operate with me in pursuing them. 



P.S. Since I wrote the above, I have repeated various ob- 

 servations on the stars and planets with a prismatic glass of 

 another kind, the adaptation of a prism to the eye glass of the 

 telescope being at all times an awkward contrivance. The re- 

 sults have varied, however, but little from those above stated, 

 and I subjoin the following rude table of the spectra of the 

 stars observed during the present month, and arranged ac- 

 cording to the intensity of light of the stars severally. 



Hartwell, Feb. 3, 1824. 



