Calendar of Flora, Fauna and Pomona. 317 



1 beg to append the following additional prismatic observa- 

 tions on the stars in March : 



March 11. — I had an opportunity, during a clear interval 

 between 11 P.M. and midnight, to resume my prismatic ob- 

 servation on the stars. A thin ami almost imperceptible cir- 

 ■rostratus or wanecloud was spread over the sky, through which 

 the light of the stars was distinctly seen, down to those of 

 the fourth magnitude. On applying the prismatic telescope 

 to the planet Mars, I found in the oblongated spectrum the 

 following coloui's. The red was very abundant and strong ; the 

 yellow considerable, the orange small; and very little violet. 

 Spica Virginis showed considerably less of the red colour, 

 scarcely any yellow; an inconsiderable quantity of green, and 

 a great deal of blue light. Vega or « Lyra: showed rather 

 more red than the last mentioned star, though considerably 

 less than Arcturus. The yellow and orange were very small, 

 indeed almost wanting ; the green very little discernible; and 

 the blue violet very plentiful: indeed this is the bluest star I 

 have yet examined. — March 13. — I observed most of the stars 

 of the first magnitude visible this evening with a higher power. 

 The Moon showed all the colours in very nearly equal pro- 

 portions. Sirius showed rather more red than on former oc- 

 casions, and some green, and also presented a large but faint 

 brush of violet*. Arcturus, a large quantity of red, of orange, 

 some green, very little of the violet. Aldeharan resembles 

 Arcturus, but has a still larger proportion of red. Betalgeus 

 like the former, but liable to assume in alternate fluctuations 

 an augmented quantity of intense red light. Jupiter all the 

 colours, but the more refrangible colours are in larger propor- 

 tions than in either the Moon or in Saturn. The large and 

 expanded violet brush has so little intensity of light, that it is 

 soon lost by the slightest cloudiness that may intervene. Mars. 

 Much red light as usual, and a considerable proportion of 

 orange. 



I cannot account for the different results of different nights' 

 observations, slight as they are, on any other principle than 

 that which I have otherwhere noticed, viz. a variation in the 

 ehromatopoietic powers of the atmosphere ; and it is to record 

 other varieties, and to call the attention of others to this vari- 



* The greater quantity of red light, it should be recollected, took place 

 in an evening in which the wanecloud prevailed, and accords with what F 

 have often before noticed. I have found on the gradual thickening of the 

 aqueous atmosphere by the wanecloud, that the colours of the spectrum 

 successively disappear in the inverse order of their refrangibility, the red 

 being seen longest. Hence the intensity of light varies inversely as the re- 

 frangibiliiv of the ray*. 



alion, 



