328 
in the use of both m.m. and mm. several times 
on the same page, and in the recurrence of 
various misspelled names. It is certainly 
amusing to learn that an article can easily be 
made by a tin smith. One notices, also, an 
occasional slip of the pen, as a result of which 
figure and text do not always agree. Thus, 
the mechanical stage, shown in figure 69, does 
not possess verniers, despite the statement in 
the description of the cut, and the absence of 
this feature is undoubtedly a serious defect in 
the construction of the stage as compared with 
that of another maker which is shown in the 
adjacent figure. The excessive number and 
length of the foot-notes in the book mar the 
beauty of the page, and many of them might 
easily have been incorporated in the text. It 
is further true that the constant use of vulgar 
fractions, which have no place in a scientific 
text-book, is another point to be justly criti- 
eised. Their employment also is not limited to 
such as are difficult to translate into decimal 
figures, but =1,, 737 mm., etc., are of constant 
occurrence, 
While it would be manifestly unfair to give 
an idea of the book based merely on these criti- 
cisms of minor details, it is evidently impos- 
sible to do more than hint at some of the many 
advantageous features which it contains. The 
synopses of the steps in the preparation of par- 
affin and collodion sections are of exceeding 
value to any student and will doubtless save 
much time and many errors. Throughout the 
book one finds very complete cross references 
and satisfactory bibliographical notes which 
will be of constant use to the worker. Every 
topic is completely and concisely discussed ; the 
order is clear and logical, and one is at a loss 
to suggest points that have been overlooked. 
The chapter on Photo-micrography deserves 
especial mention. It includes much that can- 
not be feund elsewhere and is altogether the 
best concise statement of the subject which is 
accessible. This chapter is worth more than 
the price of the entire work. Like the rest of 
the book, it is copiously illustrated ; the figures 
are exceptionally well chosen, and among them 
area couple of splendid photo-micrographs from 
the work of Mrs. Gage, who also drew all the 
original figures by which the work is illustrated. 
SCIENCE. 
[N. 8. Vou. VI. No. 139. 
As a whole, the work is a useful and valuable 
addition to the manuals accessible to the 
American teacher and is destined to be widely 
and generally used. 
HENRY BALDWIN WARD. 
The Chances of Death and other Studies in Evo- 
lution. KARL PEARSON. Edward Arnold, 
London and New York. Vol. I., pp. ix+ 
388 ; vol. II., pp. 460. $8.00. 
Professor Pearson’s essays and lectures fall 
into three groups. One of these is concerned 
with the theory of deviations from the mean in 
its application to vital and social phenomena, 
another with a criticism of certain popular 
writers who have exploited science for the 
benefit of religion and politics, and the third 
with studies in folk-lore and folk-customs, 
viewed from the light they cast on the evolu- 
tion of society. All of the essays are of great 
contemporary interest, and have to a consider- 
able degree the unity claimed by the author, 
‘the endeavor to see all phenomena, physical 
and social, as a connected growth, and describe 
them as such in the briefest formula possible.’ 
The essays on variation in this volume, and 
the series of papers on the mathematical theory 
of evolution published in the Transactions and 
Proceedings of the Royal Society since 1894, 
represent a scientific advance of great impor- 
tance. Modern science pursues two main meth- 
ods; it is either quantitative or genetic. The 
exact sciences have found in measurement a 
method of description so efficient, economical 
and universal that it must be regarded as the 
goal of those sciences in which description is only 
qualitative. The genetic method has, however, 
since the publication of the ‘ Origin of Species 
by Means of Natural Selection,’ demonstrated 
its validity. Could we add to the genetic 
method of natural science the quantitative 
method of exact science a great advance would 
be assured. 
It is not possible to describe in a few words 
what has in fact been accomplished since Quet- 
elet applied the Gauss theory of the distribu- 
tion of errors to vital phenomena. If any trait, 
such as the height of men, depends on a great 
number of small causes, some tending to make 
them smaller and an equal number tending to 
