= > 
—————- ~~ 
Deteuern 28, 1916] 
trigonometrical functions, the equation of time, 
and the declination of the sun. 
(2) The author of this little book on the rudiments 
of astronomy has endeavoured to avoid dealing 
with matter already treated in other books of 
the Hoepli series (entitled “Astronomy,” ‘ Gravi- 
tation,” etc.) by explaining mainly the apparent 
phenomena on the celestial sphere. The word 
cosmography is thus used in a sense which is 
scarcely the usual one, as descriptive astronomy, 
astrophysics, and the orbits of the planets are 
omitted altogether; but phenomena like the libra- 
tion of the moon and the tides are briefly described. 
Beginning with the figure of the earth and its 
daily rotation, the author passes on to the apparent 
annual motion of the sun, defines parallax, both 
daily and annual, and gives a table of twenty- 
seven stars the annual parallaxes of which are 
supposed to be best known, ranging from a Cen- 
‘tauri with o76” down to Polaris with o'o07”. 
The motion of the earth comes next, after which | 
precession and nutation are briefly alluded to, and 
aberration more fully. The distances and periods 
of the satellites of the planets (including the 
recently discovered ones) are given in tabular 
form, but the motion of the moon and the effects 
of its principal perturbations are described in 
greater detail. The treatment of every subject 
throughout the book is concise; the explanations 
are given in simple and unadorned language, and 
ought to give beginners a clear idea of the prin- 
cipal phenomena of the heavens within the limits 
the author has set for himself. 
OUR BOOKSHELF. 
British and Foreign Marbles and other Orna- 
_ mental Stones: a Descriptive Catalogue of the | 
Specimens in the Sedgwick Museum, Cam- 
bridge. By J. Watson. Pp. x+485. (Cam- 
bridge: At the University Press, 1916.) Price 
5s. net. 
Tue Sedgwick Museum, Cambridge, is indebted 
to the industry of Mr. Watson for its useful ex- 
hibit of polished marbles. This volume, which 
is supplementary to the one by the same author 
on “Building Stones,” is essentially a descriptive 
guide to the marbles and other ornamental stones 
in the collection, about eight hundred in number. 
The specimens have been assembled from many 
parts of the world, and a number of well-known 
varieties are represented, as well as some that will 
be less familiar. 
The geological arrangement adopted in the 
companion book has been wisely discarded in 
favour of a geographical one, but a short account 
of the distribution and geology of the marbles 
prefaces the detailed catalogue of each country’s 
products. 
As a handbook to the collection this volume is 
admirable; the descriptions are clear and, on the 
whole, adequate, and the remarks on the examples 
to be found in buildings have been prepared with 
care, but the major title is rather misleading, for 
as a work of reference its utility is lessened by 
NO. 2461, VOL. 98] 
NATURE 
327 
the circumstance that it deals only with speci- 
mens which happen to have been acquired by the 
museum. ‘Thus steatite is represented only from 
Central Africa and India, and while there is a 
considerable amount of space devoted to fluor- 
spar and jade, there is no reference to chalcedony. 
Again, dolerites and felsites are represented by 
only a single sample of each, from India, and only 
two porphyries are mentioned. In view of the fact 
that so many of the igneous rocks are used 
primarily as ornamental stones, the inclusion of 
these few examples serves merely to emphasise 
the omission of the others. 
Here and there statements of doubtful accuracy 
appear, as in the suggested coral origin of Rose- 
wood marble; and some of the information is a 
trifle stale—for example, the remarks on the popu- 
larity of Derbyshire black marble. 
The index is good and greatly enhances the 
value of the book for general use, but for practical 
purposes a list of the marbles grouped according 
to their prevailing colour should be added in 
another edition. 
A Fairy-tale in Physics. 
With seven illustrations by 
(London: Society 
Knowledge, n.d.) 
The Rain-children. 
By T. H. Orpen. 
C. E. Brock. Pp. vi+112. 
for Promoting Christian 
Price 2s. 6d. 
In designing the plan of this book the author 
seems to have thought of the nursery expedient 
of administering a medicinal powder in a spoon- 
ful of jam. His object appears to be to explain 
to children the formation and uses of the forms 
of water, but, having doubts of the intrinsic in- 
terest of the subject for his readers, he creates 
characters like Aunt Cold, Aunt Heat, Colonel 
Lightning, Sergeant Thunder, and Rain-children 
to describe to a little heroine he has created how 
natural phenomena can be explained. The result 
is a tale which little girls may like, but we be- 
lieve boys usually prefer to keep their lessons and 
stories for separate occasions. 
LETTERS TO THE EDITOR. 
[The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications.] 
University Doctorates. 
I see from an announcement in the Times of Decem- 
ber 22 that facilities are to be offered to advanced 
students of other universities by the University of Ox- 
ford in order to allow them to take the degree of 
Doctor of Science or of Doctor of Letters under new 
conditions. 
It is to be hoped that, before any such scheme is 
discussed, a serious attempt may be made to introduce 
something like a uniform standard of attainment 
among our own universities for the doctorate, which is 
at present awarded for very different degrees of attain- 
ment and under very different conditions. When that 
uniformity has been adopted, any scheme offering 
facilities for the doctorate to graduates of the United 
