268 
NATURE 
[JANUARY 21, 1904 
Suffolk and Berkshire, reference is made to the now 
almost forgotten fact that no later than the first half 
of the last century many of these hounds—and we 
presume fox-hounds also—were whole-coloured, in- 
stead of being of the tripartite ‘‘ hound-colour ’’ with 
which we are now familiar. Reddish was the pre- 
valent tint, with a tinge of brownish-grey along the 
back, so that the hound was very similar in colour to 
the hare of which it was in pursuit. This, of course, 
has an important bearing on the ancestral stock from 
which our modern hounds are derived, and tends to 
confirm the view of Bell as to the derivation of these 
animals from a bloodhound stock. 
As the editor admits in his preface, some objection 
might legitimately be raised to the inclusion in the 
volume of an article by Lord Delamere on lion-shooting 
in East Africa, and of another by Lord Walsingham 
on Spanish ibex hunting, since if these are admitted 
it is somewhat difficult to see why big game shooting 
in general was not included. Taking, however, the 
facts as they are, we find some very interesting points 
in Lord Delamere’s narrative—notably the statement 
that wart-hogs, when chased by lions to the deserted 
aard-vark holes, in which they often take up their 
abode, invariably enter backwards, so as to present 
their formidable tusks to an assailant. In the course 
of his account of a hunting trip to the haunts of the 
Spanish ibex, or wild goat, Lord Walsingham records 
many interesting points in connection with the fauna 
and Hora of the districts traversed. 
With this we take leave of an attractive volume 
which oucht to occupy a handy position in the library 
of every British sportsman Raw: 
OUR BOOK SHELF. 
Theoretical Mechanics. An Elementary Text-book. 
Second edition. By L. M. Hoskins. Pp. xi+456. 
(Published by the author, Stanford University, Cal., 
1903.) Price 3 dollars. 
WE have here a very clear and lucid exposition of the 
fundamental principles of mechanics, presented always 
with incisive logic, in a simple manner, and enforced 
and illustrated at frequent intervals by well selected 
cexemples. 
The book is divided into three parts, of which the 
first deals with statics, and includes a chapter on gravi- 
tation and the attraction of spherical shells. The 
second part is concerned with the dynamics of a 
particle, and part iii. treats of the motions of systems 
of material particles and of rigid bodies. 
The subject is treated mainly by analytical methods, 
an elementary knowledge of the calculus being 
assumed. But the vector nature of the subject is 
always kept prominently to the fore, and the vector 
significance of the various terms in the dynamical 
equations is brought well home to the student by ample 
illustrations and descriptions. The book opens with 
a special chapter on vectors, and vector equations are 
freely employed throughout, verging sometimes on the 
use of vector products, as, for instance, when establish- 
ing the relations which exist amongst the various 
quantities in the case of the transformation of axes in 
the instructive chapter on relative motion which con- 
cludes the volume, and which has been added since 
the first edition. 
Attention is mainly confined to motion of translation 
NO. 1786, VOL. 69] 
in space, and to the general case of plane motion, 
general motion in three dimensions being only casually 
alluded to. This seems to us a wise arrangement, as, 
in the space available, it allows the treatment to be 
very full and complete. 
The C.G.S., the poundal-pound, and the “ en- 
gineers’’’ systems of units are all clearly explained. 
The author, however, seems to be under some mis- 
apprehension as to the unit of force in the engineers’ 
system. He says this varies with the locality on 
account of the variation of gravitation, but that the 
system could be made dynamical by specifying the 
locality. In this country, at any rate, such specifi- 
cation is made, and the engineers’ system is thus as 
strictly absolute as the C.G.S. or the poundal-pound 
systems. 
Considering the importance of harmonic motion in 
its many applications, as in electricity, in problems on 
balancing, in harmonic analysis, &c., many readers 
would have welcomed a special chapter devoted to the 
subject, including some reference to rotating vectors. 
In a treatise like the present, it would seem highly 
desirable that a short account of the experimental 
verification of fundamental laws should be given, and 
the student be directed to carry out the experiments 
personally in the laboratory. But there is little room 
for adverse criticism in this most excellent text-book, 
which is one of the best on the subject that has recently 
appeared, and cannot fail to give satisfaction wherever 
used, 
Atlas des Erdmagnetismus fiir die Epochen 1600, 
1700, 1780, 1842 and 1915. By Dr. H. Fritsche, 
Director emeritus des K.R. Observatoriums in 
Peking. (Riga: Miillerschen Buchdruckerei, 1903.) 
Tuts work consists of a series of charts of equal lines 
of magnetic declination, inclination, and horizontal 
force for the five epochs 1600, 1700, 1780, 1842 and 
1915, calculated by the author with the assistance of 
the Gaussian theory. 
In his introduction he discredits the accuracy of the 
charts of the epochs hitherto published by Hansteen, 
van Bemmelen, Sabine and others as being the results 
of observation only, many of such observations being 
defective, and the lines drawn without the help of any 
theoretical groundwork. There is a mistake here as 
regards Sabine’s charts of the Arctic and Antarctic 
regions, as the Gaussian lines calculated for 1840 were 
largely used in their construction. Nevertheless, the 
author has spared no pains in his endeavour to replace 
what he condemns by something better, hence the pre- 
sent charts. 
Considering the existing knowledge of terrestrial 
magnetism as regards the secular change of the mag- 
netic elements, and our limited knowledge from 
observation of the conditions in the southern parts of 
the earth, the author appears to be somewhat pre- 
mature in providing charts of inclination and force for 
the epochs 1600 and 1700, especially when so little was 
known of either element before the early years of the 
last century. 
From the lengthened period during which the de- 
clination has been observed, the means exist for com- 
paring the theoretical results of these calculated charts 
with good normal observations. Thus at Cape Town 
we find for the epochs 1842 and 1915 a difference in 
declination of —1°.5 and +2° respectively, and at other 
well-known places similar differences. 
Again, these charts indicate that the north magnetic 
pole moved in a south-easterly direction nearly 700 
miles in the 315 years since 1600, some 93 miles of 
these being traversed between 1842 and 1915, whereas 
observations during the latter period indicate that the 
pole moved in a north-westerly direction. The south 
