74 
NATURE 
[NovEMBER 26, 1903 
ment of a butterfly emerging from the chrysalis, cater- 
pillars feeding, the webs or tents woven and leaves 
curled up by caterpillars for their protection, and 
various insects in natural attitudes. We hardly think 
that ‘‘ mourning-cloak butterfly ’’? (under which name 
the life-history of this butterfly is ably dealt with) is 
any more happy than Camberwell Beauty. To read 
this dainty volume is to get a fair knowledge of the 
elements of entomology in a very pleasant way. 
““The Brook Book,’’ on lighter paper than the two 
volumes of this series just noticed, consists of a number 
of chapters describing the plants and live creatures to 
be met with in rambles along the banks (and in the 
bed) of brooks. Some of them relate the doings of a 
college walking party which explored their neighbour- 
hood, and the occasional introduction of a professor or 
a “visiting geologist ’’ leads to informing chapters, 
while the adventures of the members themselves add 
a vein of humour. It is impossible even to state the 
wide range of subjects so pleasantly dealt with, but 
they cover the settings and occupants of various kinds 
of brooks; and the enthusiasm of the writer and her 
pleasant way of introducing the subjects make the 
book just the thing to read aloud to elder children, and 
to instruct oneself with at the same time. The sixteen 
half-tone plates of brook scenery are very beautiful, 
and there are nearly seventy line engravings in the 
text. 
We have in a volume of the American Sportsman’s 
Library a capital guide to the waterfowl of North 
America, at once readable and scientific, and useful 
alike to the naturalist and the sportsman. Introduc- 
tory chapters treating of the structure, character of the 
plumage, migrations, and the use as food and orna- 
ment of these groups, and of the necessity of affording 
them protection in spring, are followed by descriptions 
of the chief stations for wildfowling and of the various 
modes of shooting ducks and shore-birds. These 
chapters are written in the graphic language of an 
enthusiastic and thorough ‘‘ workman.’’? The details 
of actual shooting days and nights, with exciting 
and amusing incidents, written with a certain 
amount of expressive ‘‘ western’? words, will appeal 
strongly to all who have felt the glamour which 
hangs about ‘‘ wildfowl.’’ The body of the book 
is taken up with a scientific description of each 
species, giving details of the different stages of 
plumage at all ages and seasons, measurements, 
eggs, and habitat, followed by a general account 
of the habits. The waterfowl of the Pacific coast 
are separately dealt with, and the book closes 
with diagnoses of the families and genera. It is 
beautifully, though not profusely, illustrated, and the 
letterpress is printed on nice light paper, which 
makes this pleasing volume not too heavy to be held 
comfortably, despite its six hundred pages. 
The object of Mr. Lange’s handy volume is to point 
out to teachers some of the material which may be 
made the basis of profitable lessons in nature-study, 
and he has endeavoured to show how this material 
may be made available, and what the pupils may be | 
taught about it. The plan here advocated is to take 
the children out into the fields and woods and to show | 
them, and let them examine, various natural objects, 
NO. 1778, VOL. 69] 
or to bring before them prepared and preserved objects 
and to instruct them in these. The teacher is told 
how best to do this. The book, indeed, consists of a 
series of lessons on various natural objects, in which 
the requisite information is given, and the teacher is 
told what material is necessary and how to obtain and 
use it. The author has been successful in producing 
a valuable manual of work for children whose school 
years close with the common school course. The 
numerous woodcuts are useful and to the purpose. 
Unfortunately for English readers the country for 
which the book is especially designed is the eastern 
States of North America. O. V. APLIN. 
THE NATURE OF ELECTRICITY AND THE 
CONSTITUTION OF MATTER. 
Conduction of Electricity through Gases. By J. J. 
Thomson; D:Sc., LL.D:, PhDs) ERIS: Epa 
566. (Cambridge: University Press, 1903.) Price 
16s. 
HIS book on the newest branch of physics, from 
the pen of its originator and chief exponent, 
deals with one of the most rapid and remarkable de- 
velopments of modern scientific .research. The 
‘‘jonisation theory of gaseous conduction,’ it is 
claimed in the preface, not only gives a simple and 
direct explanation of the electrical properties of gases, 
but also affords the means of subjecting the funda- 
mental problems of the nature of electricity and the 
constitution of matter to direct experimental attack. 
The reason is very clearly set forth. 
““The possession of a charge by the ions increases 
so much the ease with which they can be traced and 
their properties studied that as the reader will see we 
kknow far more about the ion than about the uncharged 
molecule.’’ 
There is food for reflection for both the man of 
science and the philosopher in this comprehensive re- 
mark. Less than a decade ago the possibility of the 
existence of a gaseous ion was hardly recognised. To- 
day this volume of very respectable dimensions testifies 
to the wealth of researches that have followed the incep- 
tion of Prof. Thomson’s theory. The researches of the 
author and his former pupils, Rutherford, Townsend, 
C. T. R. Wilson, Zeleny, Strutt, H. A. Wilson, 
Langevin and many others are brought together in 
this book and correlated with older researches and 
with those that have been proceeding simultaneously 
elsewhere. 
In the two opening chapters the fundamental posi- 
tion is developed that the charge carried by the gaseous 
ion is the same for the ions of all gases, is independent 
of the ionising agency, and is equal to that carried 
by the hydrogen ion in electrolysis. This conclusion 
is arrived at from considerations of the diffusion 
velocity of the ions, and their velocity in an electric 
field, and needs only the assumption that the ions 
behave like the particles of a perfect gas towards 
pressure. 
A second and completely independent determination 
of e for the same kind of ions is made possible by the 
application of the condensation experiments af C. T, R. 
