72 Astronomical Society: the Astronomer Royal 
chemical and physical ; whilst others can only he called into play 
under conditions of a more complex nature, which are only supplied 
by a living organized system, where many particles being combined 
by a previously- existing life into one structure, exhibit actions of a 
peculiar character, dissimilar to any they have heretofore presented, 
which are denominated vital. 
The dependence of life upon external stimuli is then pointed out, 
and a great variety of interesting facfs, many of them novel, are col- 
lected, relative to the influence of heat, light, and electricity upon 
living beings. The general laws which have been ascertained to 
govern the structure and actions of organized beings are then enun- 
ciated, and their application illustrated by examples. To pursue 
their application through the whole range of the animal and vege- 
table kingdoms is the object of the second book, entitled Special 
Physiology. Here each function is considered in detail, in the va- 
rious phases under which it appears in the ascending scale both 
of the vegetable and animal kingdoms; the fundamental unity 
which prevails throughout is displayed ; and the very extraordinary 
correspondence which exists between the transitory states of dif- 
ferent organs in the embryo condition of the higher classes of each 
kingdom, and the permanent forms of the same in the lower, is de- 
monstrated in a striking and satisfactory manner. This part of the 
volume is illustrated by a large number of well-executed figures, 
which greatly aid the comprehension of the text. 
The author appears to us to have fulfilled his design in the most 
satisfactory manner ; and as his work has been received with high 
approbation by the Medical Press, we can feel no hesitation in re- 
commending it to our scientific readers as the one best calculated 
to imjDart to them a sound knowledge of the principles of physio- 
logy. We may add, that the clearness of its style, and the simple 
manner in which the highest truths on this deeply- interesting sub- 
ject are presented to the student, render it not only a useful, but an 
agreeable book to any reader of ordinary intelligence. 
XII. Proceedings of Learned Societies. 
ROYAL ASTRONOMICAL SOCIETY. 
N'ov. 8, following communications were read : — 
1839. On the Determination of the Orbits of Comets, from 
Observations. By G. B. Airy, Esq. Astronomer Royal. 
The author begins by remarking, that the generality given by 
Laplace to the investigation of the orbits of comets is so complete, 
and tlie variations on the method introduced by other writers so 
numerous, that, as regards generality and facility, the subject may 
probably be considered as exhausted. The method which is de- 
veloped in the ])resent Memoir professes to be merely a modifica- 
tion of Laplace’s method, directed by considerations of a purely 
practical nature, which arc known to the working astronomer ; but 
