166 Trausactions, — Miscellaneous. 



serve to give us a certain amount of information that can be thoroughly relied 

 on ; they enable us to state, further, that the existence of certain physical 

 conditions, and the presence of certain elementary substances in certain 

 stars, are highly probable ; and, possibly, they are calculated to create or 

 stimulate in us a desire to learn more certainly and fully the constitution 

 and physical habitudes of the stars. 



The objects are treated of in the order of their Eight Ascension, and 

 the places of the stars, when given, are taken fi"om the "Fu-st Melbourne 

 Catalogue," epoch, 1870. 



The first star on the list is Achernar, or a Eridani. This fine first 

 magnitude star is very nearly pm*e white, without any discernible tint, 

 except possibly a slight shade of blue. This star belongs to Padre Secchi's 

 first class of stars, the type of which is the giant sun Sinus. In the 

 case of typical stars of this class, the spectrum is remarkable for the great 

 breadth and distmctness of the hydrogen lines. Indeed these stars are for 

 convenience often called "the hydrogen stars." All of them are white, or 

 bluish-white. In Acheryiar the hydrogen lines are not nearly so strongly 

 marked as they are in some others of the class. Indeed the star by no 

 means nearly approaches the type, and is probably to be considered as 

 holding a position between such stars as Sirius and stars of the second 

 class, like Procyon, though much nearer to the former than to the latter. 



TT Eridani. — This beautiful little double-star is just visible with the naked 

 eye in fine weather. It is about one degree from Achernar, north follow- 

 ing. The two components are of the same orange colour, and of very 

 nearly equal magnitudes, 7 and 7. When Sir John Herschel measm-ed 

 this star (anno 1835-0), he found the angle of position with the meridian to 

 be 122-3°. Powell, in 1863, found the angle to be 73-9°. Last week (say, 

 anno 1879*75) the angle was 58-8°. The distances for the same dates are 

 3-65", 4-88", and 5-3". This interesting double is, therefore, very probably 

 a binary star of comparatively short period. 



Eridani.— R. A. 2hrs. 53min. 19-9 sees. Decl. 40° 49'~35' 17" S. In 

 the Melbourne Catalogue, the magnitudes 5-2 and 6-2 are assigned to the com- 

 ponents of this fine double star. There is most certainly serious error here. 

 The star is plainly, taken as a whole, a large fourth, or a small third-mag- 

 nitude star. Probably magnitude 3-9 for the larger star, and 5-9 for the 

 smaller one, would not be far from the truth. The colour of the larger 

 star is yellowish -white, with a faint green tinge ; the smaller is a light 

 shade of indigo blue. Sir John Herschel's angle of position and distance, 

 in the year 1835-75, were 81-6° and 8-68". The angle at the epoch 1879-75 

 is 85-4°. I have not been able to get a thoroughly satisfactory distance, 

 but it is now somewhat over 10". Time and accumulated observations will, 



