56 PROCEEDINGS OP THE ACADEMY OF 



corded change simply because it is small, would therefore be a real misrepre- 

 sentation of the case, and a virtual falsification of the records. Moreover, 

 the colors as they stand recorded are from experienced observers, men whose 

 lives have been devoted to an accurate representation of facts, who do nothing 

 without care and deliberation, and whose common and avowed practice is not 

 to record any color when the atmosphere is not favorable for such obser- 

 vations. 



As already stated, there are difficulties in deciding on colors by the naked 

 eye when the star is not large, and when the departure from white is small. 

 But this difficulty is not in the way of large stars, as Arcturus and Sirius ; 

 nor does it apply to the telescope, except in the very smallest magnitudes. To 

 decide between two different colors, such as red and blue, is never difficult ; 

 and when two colors are blended, it is the custom to name them both, a3 bluish 

 green, reddish yellow, and the like. The disturbing effects of the atmosphere, 

 or of the instrument, may be detected either immediately or after several nights 

 of observation. The atmosphere cannot color one star and leave all the other 

 stars in the same neighborhood uncolored. The telescope cannot act pecu- 

 liarly on any one star ; it must treat all alike, especially of the same magni- 

 tude and color. Simple comparison is therefore an admirable test ; and another 

 important test is time watchfulness every night through different changes of 

 weather. If hereafter even this shall not beVound satisfactory in any one locality, 

 then simultaneous observations at widely distant places will most certainly 

 eliminate all suspicion of mistake. For instance, observations may be made 

 at Australia, the Cape of Good Hope, and Chili in the southern hemisphere; 

 and in the northern hemisphere both on the Pacific and Atlantic coasts of 

 America, on the Atlantic coast of Europe, in Russia, and in Hindoostan. If 

 the star shall prove of the same color at all these different regions at the same 

 time in favorable weather, then that color may be regarded as unquestionable. 

 Even by using one locality alone absolute certainty may be acquired, as the 

 red colors of Aldebaran, Betelgueze, and Antares. The same certainty may 

 be looked for hi this as in other departments of astronomy, and even greater 

 certainty than in many. There is an uncertainty, in opinions of wise men, of 

 three millions of miles in the distance of the earth from the sun ; and yet this 

 uncertain distance is used as a measuring line to fathom other and far greater 

 distances. But this uncertainty to so large a degree does not take away from 

 the supreme value of the determinations nevertheless. These determinations, 

 with all their known reservations, are held as of the highest importance. So 

 in the colors of the stars ; mistakes may be made, the intermixtures of 

 error may certainly exist, though we cannot tell exactly where they are, and 

 yet the present recorded observations are precious beyond estimation. And a 

 time is coming when simultaneous observations from various positions in both 

 hemispheres will render them beyond suspicion. To hasten on this time we 

 have only to make good use of the materials already on hand. 



Why the changes in the colors of the stars are not more frequently observed, 

 was pointed out in a former communication. Why the belief in their real oc- 

 currence is hard to be admitted, and why their observed changes are ascribed 

 to supposable errors from the instruments, from the atmosphere, and from per- 

 sonal deficiencies, seems to arise from the opinion that such vast bodies cannot 

 possibly undergo great changes in a shoit time. But this opinion rests on do 

 known scientific grounds. When fairly viewed, the fixedness of the colors of 

 the stars should not seem more likely than the fixedness of their positions. 

 Indeed the two ideas are very much alike. In ancient phrase, the stars were 

 said to be " rivetted " to the vault of heaven. Now we know from observations 

 more refined that many of them move, and we have a conviction, from the na- 

 ture of attraction, that they must all move. In like manner, in a universe 

 where every known object is subject to change in various ways, our first ideas 

 should be that the colors of all the stars must change. Hence we should ap- 

 proach the recorded changes with favorable judgments. If we are to have any 



[March 



