Notices respecting New Books. 571 
for the student but for the working astronomer. It is from the 
point of view of the student that we consider the book here. The 
three opening chapters form. Part I., and are devoted to preli- 
miuary questions such as the meaning and use of small quantities, 
interpolation, and determination of probable errors. Chapters IV. 
to IX., which constitute Part II., deal with the fundamental prin- 
ciples of spherical astronomy, and discuss in order spherical co- 
ordinates, measurement of time, parallax and figure of the eirth, 
aberration, astronomical refraction, and precession and nutation. 
Having thus laid the foundations strong and sure, Prof. Newcomb 
proceeds to consider in the four remaining chapters which make 
up Part III. the reduction and determination of positions of the 
fixed stars. The value of this part is enhanced by the fact that 
real examples are worked out in full as illustrations of the methods 
described. At the end of each chapter is appended a set of 
historic notes which give with great conciseness the important 
lines of development. Where all is so admirable it is difficult to 
pick out particular points for special reference. The discussion 
of astronomical refraction seems, however, to merit special notice. 
The treatment is fresh, and should be read by all mathematical 
and physical students, even although they should have no intention 
to pursue astronomical studies further. 
Meteorohgische 0_ptilc. Von J. M. Pebxter. III. Abschnitt. 
Wien und Leipzig : W. Braumuller. 1906. Pp. 346. 
In this volume the author continues his exhaustive account of 
meteorological optics. The first section of this monumental work 
appeared in 1902, and was soon followed by Section II., which 
appeared later in the same year. Both were noticed briefly in 
these columns. Section III., now under review, deals with 
phenomena produced by particles not always present in the 
atmosphere — ice crystals and water-drops of clouds and rain. This 
section of the work is divided into three chapters, the division 
being based on the particular effects to which the phenomena in 
question are due. Thus, Chapter I., which fills the greater part 
of the volume, deals with phenomena caused by refraction and 
reflexion — halos and parhelia. Numerous illustrations and 
accounts of some very remarkable instances of: such appearances 
are given, and a very thorough classification of snow crystals, with 
numerous plates illustrating their different forms, is incorporated 
in this chapter. Chapter IT. treats of phenomena due solely to 
diffraction — coronas and similar effects, while Chapter III. is devoted 
to rainbows, The same thorough method of treatment is followed 
by the author throughout. "We first have a descriptive account of 
the appearances dealt with, then a detailed theoretical explanation, 
and lastly an account of experimental arrangements which enable 
us to reproduce the effects dealt with, and to supply a test of the 
soundness of the theoretical explanations. To the student of 
meteorological optics this work will be full of interest. 
