98 PROCEEDINGS OF THE ACADEMY OF 



meeting, Feb. 17th, he convinced himself that his impression was wrong, 

 and that the present real color of Sirius is green ; and he obtained consent 

 that the Minutes, when printed, should be altered accordingly ; but by some 

 oversight this alteration was not made. In denominating Sirius purple in 

 October last, I dissented, for it appeared to me plainly green. The three 

 successive, undisputed colors of Sirius therefore are red, white and green. 

 There is special need of attending to discrepancies in the beginning of this 

 catalogue, both as to color and to dates. This is the only way to insure pro- 

 gress. 



It is to me an impressive fact that so many conspicuous stars now nightly 

 appear blue or green ; especially as the first blue stars were mentioned by 

 Mariotte, so lately as in 1686 ; before him, no departure from white was 

 named but red, with the exception of the yellow in the temporary star of 1572. 

 Capella, Bellatrix, Rigel, Procyon, Vega, Beta Librae are blue ; all deeply so 

 except Capella and Vega. Sirius is conspicuously green, and Castor slightly 

 green, though I sometimes doubt the greenness of the latter. When a star 

 is not of the first magnitude, or when its departure from white is not very de- 

 cided, a long fixedness of the eye upon it is necessary, and a careful exclusion 

 of artificial lights. At least, this is my experience. It has occurred to myself, 

 and been suggested by others, that perhaps this blueness of so many large 

 stars now in view, and greenness, which is a modification of blue, may be 

 owing to some special atmospheric cause. For many months the air has been 

 unusually damp. But this cannot be the cause of these colors, for Aldebaran 

 Betelguese and the planet Mars are in the midst or near vicinity of some of 

 these blue and green stars, and preserve their ordinary redness. Pollux, how- 

 ever, in the same general neighborhood, seems hardly entitled to be called a 

 red star. From the fact that it was classed among the six decidedly red stars 

 by the ancients, I regard it as changed, but desire further time before announc- 

 ing the change in the catalogue. Humboldt calls it merely " reddish." 



I would not be premature in speculating on the laws or causes of these 

 changes, but must remark that the change of Sirius, from its ancient red to 

 white, and now to green, is all in the same direction, namely : a relative 

 diminution of the red. The three primary colors, red, yellow and blue, with 

 an excess of red, will give a red star ; take away the excess of red and the 

 star will be white ; take away still more of the red and it will be green, that 

 is, a combination of the remaining yellow and blue. The three colors of 

 Sirius, therefore, the ancient red, the modern white and the recent green, may 

 possibly be due to the operation of a single cause. 



Communication, March 2<lth. 



Mr. Cassin read the following interesting extracts from a letter to Prof. R, 

 Dunglison, of this city, from Dr. James A. Grant, of Ottowa city, Canada, 

 dated Feb. 10th, 1863, relating to the Willow Grouse, or Ptarmigan, Lagopus 

 albus : "During the present winter, the Ptarmigan or White Grouse has been 

 observed in large numbers at the head waters of the Gatineau river, (a tribu- 

 tary of the Ottowa river,) distant from Ottowa city about 120 miles. In that 

 locality, lumberers are constantly engaged, who have, this season, procured 

 these birds in considerable numbers, a very unusual circumstance, as years 

 frequently elapse without one being observed. This bird seems to be guided 

 in its migration by peculiarities of climate, and is only seen in this particular 

 locality when the season is very cold. Since the year 1844 it has not been 

 observed by the lumberers until the present season, and it seems that noth- 

 ing short of excessive arctic cold will bring it from its more northern abode." 



"It is stated by Buffon that the Ptarmigan avoids the solar heat, and pre- 

 fers the biting frost on the tops of mountains. These peculiarities I have 

 also observed here. This bird appears to enjoy the soft snow on the hill sides, 



[April, 



