200 Notices respecting New Books. 
To find the position o£ F, the lens L is removed and a 
screen S is adjusted until an image of it is formed in the 
focal plane of the telescope T. As in the previous methods, 
the focal length required is the distance between L and F. 
In this experiment an auxiliary convex lens L 2 may be 
employed, if necessary, so that F may be brought to within a 
short distance of the telescope. 
Of these methods II. and III. appear to be more accurate 
than I. 
Technical College, Bradford. 
Oct. 1907. 
XIV. Xotices respecting New Books. 
Reclierclies sue tes Proprietes Optiques des Solutions et des Corps 
Dissous. Par M. C. Ceecteveatj. Paris : Gauthier-Villars. 
1907. Pp. 190. 
nnHIS memoir forms the thesis presented by the author for his 
-*- Doctorate to the University of Paris. It contains the results 
of numerous determinations of the refractive index and dispersive 
power of various solutions (aqueous and others), and the conclu- 
sions deduced by the author from the results of his experiments. 
The apparatus employed by him consisted of a modified form of 
Fery refractometer. It is interesting to note that according to 
the author's researches there is little to choose between the law 
of Gladstone and that of Lorentz, although the latter appears to 
give rather more accurate results when dispersion is taken into 
account. Students of physical optics will find a great deal to 
interest them in this valuable contribution to our knowledge of 
the optical properties of solutions. 
Rivista di Scienza. Anno I (1907), No. 1. Bologna: Nicola 
Zanichelli. 1907. Pp. 192. 
The first issue of this new periodical, which is described as an 
" International Review of Scientific Synthesis," contains the 
following articles : — "La mecanique classique et ses approxima- 
tions suceessives," by E. Picard ; " Zur modernen Energetik," 
by W. Ostwald ; " Problemi di chimica organica," by Gr. Ciami- 
cian ; " 11 concetto di specie in biologia," by F. Raffaele ; " Die 
natiirliche Zuchtwahl," by H. E. Ziegler ; " II carattere delle 
leggi economicbe," by C. Supino ; " Impartiality in History," by 
W. Cunningham ; " Questions pedagogiques," by J. Tannery. 
In addition to these, there are reviews (in Italian) of various 
scientific works, and of recent progress in various departments 
of science. The scope of the new periodical, it will be seen, is 
