3S8 Ohsei^mtions 0 Stars. 
77. ^ Aquarius. R.. Asc. 22^ 19'. N. Decl. O'" 57'. 
4th Mag. and 4th-5th Mag. 
This star is well known. Sir W. Herschel says that the two 
are equal. M. Struve considers the most northern as the small- 
est, and distant from the other a diameter of the star. The fol- 
lowing are the angles of position : 
1779.9, 
- 
7r 
5' N. -Foil, 
- 71° 
5' Herschd. 
1781.7, 
- 
71 
39 
71 
39 Ditto. 
1784.5, . 
- 
72 
7 
- 72 
7 Ditto. 
1802.0, 
- 
78 
3 
78 
3 Ditto. 
1819.6, 
- 
88 
0 N. Free. 
= 92 
0 Struve. 
The motion in the angle of position seems to have accelerated. 
Before 1802, it had changed 58' in 22.1 years ; but after 1802, 
it changed IS'" 57' in 17.6 3 ^ears. 
Akt. XXIV. — Observations on the Comparative Anatomy of 
the Eye. By Robert Knox, M. D. F. R. S. Ed., &c. &c. 
In the volume of the Transactions of the Ro^’^al Society of 
Edinburgh, which has just appeared, Dr Knox has published 
an elaborate Memoir on the Comparative Anatomy of the Eye, 
of which the following is a brief abstract. 
In the first section of the Memoir, Dr Knox has consider- 
ed the subject of vision generally, examining carefully the opi- 
nions of some very distinguished physiologists, and more parti- 
cularly those of Baron Cuvier. It appears to Dr Knox, that 
we owe to Dr Porterfield the opinion, admitting almost of de- 
monstration, that within certain limits, perhaps within the range 
of very distinct vision, our knowledge of distance is perfect, 
and depends on the organ being double and symmetrical. Be- 
yond this point, which in man is very limited, the mode by 
which we judge of distance becomes complex ; we avail ourselves 
of other senses, more particularly that of touch, and thus ac- 
quire experience. 
Without doubt the faculty by which the same individual 
may distinguish the same object at different distances, whilst it 
is the most important function of the eye-ball, is the one most 
difficult of explanation. It is evident that the eye must have 
