m 
Natural Philosophy.— Optics. 
of his observed places of the heavenly bodies, as well as in ad- 
justing the position of his instruments, and deducing his correct 
time. The second volume will contain an account of the various 
instruments at present used in making astronomical observations, 
illustrated by numerous engravings by Turrell, done in his best 
manner ; and the methods of using the instruments will be ex- 
emplified by applying the corrections, derived from the Tables, 
to real observations made with the instruments described. A 
work like this has been long wanted ; and we know of no person 
better qualified, by his talents and his practical knowledge, for 
such a work, than Dr Pearson. The council of the Astronomi- 
cal Society have given the author permission to have his labours 
dedicated to its President, Vice-President, and Members. 
8. Changes in the Declinations of ' some of the Fixed Stars.— 
In the Phil Trans . for 1823, part I., Mr Pond has published a 
series of observations, from which he deduces a change of decli- 
nation southwards, which is not explained by the received doc- 
trines of astronomy. This discovery will be a most important 
one, if Mr Pond confirms it by his future observations ; but we 
understand that this anomaly is not deducible from the contem- 
poraneous observations of that able astronomer, the Reverend 
Dr Brinkley. 
OPTICS. 
9. Paranthine and Wernerite . — -Although these two minerals 
have been given in Treatises on Mineralogy as different species, 
yet mineralogists have conjectured, that, from the similarity of 
their crystalline forms and chemical composition, their identity 
would be proved by future analyses. Dr Brewster has lately 
examined the optical structure of the Paranthine from Christian- 
sand in Norway, which Dr Forchhammer of Copenhagen was 
so good as to send him for this purpose, and has found it to be 
the same as that of Wernerite. It has one axis of double refrac- 
tion, coincident with the axis of the square based prism, in 
which it crystallises. The action of this axis is negative, like 
that of Wernerite, and the character of the tints is exactly the 
same. 
10. On the Defective , Vision of the Hors s e .— The following 
very curious facts are mentioned by Dr Knox, in his valuable 
