150 
NAL OIE 
[ DECEMBER 17, 1903 
ments, but at the same time in this, as in so many 
other cases, we hold that statistical methods cannot 
be safely used without proper training. Experi- 
ments of a most laborious character may be rendered 
nugatory because the observer has not started with a 
clear conception of what statistical processes he is going 
to employ to deduce his results, nor what observations 
are needful if any conclusions at all are to be reached 
by legitimate numerical arguments. The book shows 
the increasing interest in the problems of inheritance 
and in biometric methods; it is characterised through- 
out by a courtesy of tone which is very pleasing when 
contrasted with some recent controversial papers on 
heredity; but it fails, and fails badly, to prove any 
definite point, because the author has not clearly stated 
his problem, and had he done so has really not the 
knowledge needful to deal effectively with statistical 
data. 
OUR BOOK SHELF. 
Die europdischen Laubmoose. By George Roth. 
Lieferung i. Band i. 128. (Leipzig: 
Wilhelm Engelmann, 1903.) 
Tue second enlarged edition of Schimper’s ‘‘ Synopsis 
muscorum Europeorum ’”’ was published in 1876, and 
a list of European mosses was given by the same 
bryologist in ‘‘ Revue bryologique ”’ seven years later. 
Since that time, in this country there have appeared 
Hobkirk’s synopsis, Braithwaite’s ‘‘ Moss-flora,”? and 
Dixon’s handbook. In other countries there has been 
the same advance in bryological records, to mention 
only Limpricht’s compilation for Germany, Austria, 
and Switzerland, and Husnot’s ‘‘ Muscologia gallica,”’ 
so that the time is ripe for a new European synopsis. 
The work undertaken by Dr. Roth is, on the one 
hand, rendered easier by the existence of these 
authentic catalogues, but meantime the number of re- 
corded species has increased, so that whereas Schimper 
enumerates goo, the author estimates European species, 
exclusive of Sphagna, at 1300; of these about 600 occur 
in Britain. 
The greater portion of this, the first part, is given 
up to a general introduction, and only the last few 
pages are concerned with the enumeration of genera 
and species. The introduction is well written, and the 
author has throughout emphasised the various 
characters which are of immediate importance for 
identification and classification. There is an original 
chapter on the part which mosses play in the economy 
.of nature, and some account of their distribution. 
The system of classification adopted by the author is 
nearly identical with that of Schimper and Limpricht, 
the critical features being the separation of Archidium 
as a special order, and the division of the Bryinez into 
cleistocarpous and stegocarpous groups; _ British 
bryologists favour Lindberg’s arrangement, in which 
the cleistocarpous mosses are split up amongst the 
other natural orders. 
In the essential systematic part of the book there 
are only a few descriptions from which to form an 
opinion. The author leads off with the Andrezacez, 
as the Sphagnacez will not be included, and he makes 
fifteen species for Andrezea; of these several are only 
accorded the rank of varieties by other authorities, e.g. 
.of the fifteen, nine have been found in Britain, and yet 
Dixon only allows at the most five species. The 
various countries from which the species have been 
recorded should, we think, be definitely stated. 
Another very desirable, indeed necessary, addition is 
NO. 1781, VOL. 69] 
Pp. 
the provision of tables to determine genera, and a 
separate species-key to each genus. The book is 
liberally illustrated, but the plates are far from 
pleasing, and the areolation of the leaves is very doubt- 
fully shown owing to the small scale adopted for the 
drawings. There are obvious advantages in using a 
general synopsis rather than, or in addition to, the 
flora of a single country, so that the book is a very 
desirable one, but it would be made more useful by 
the insertion of analytical keys and critical notes deal- 
ing with the more doubtful species. The book is to 
be issued in eight parts at a cost of about three pounds. 
Mechanics, Molecular Physics and Heat. By Robert 
Andrews Millikan, Ph.D. Pp. 242; diagrams. 
(Boston and London: Ginn and Co., 1903.) 
Price 7s. 
Tu1s book represents the first portion of a college 
course in general physics, in which the primary object 
has been to establish an immediate and vital connec- 
tion between theory and experiment. It has, there- 
fore, been made neither a laboratory manual, in the 
ordinary sense of the term, nor yet a simple class- 
rocm text. Each section is introduced by a theoretic 
statement, and is followed by instructions with regard 
to an experiment to be performed. As it is only a 
twelve weeks’ course which is represented, the experi- 
ments have had to be selected out of the large number 
of possible ones, and in making this selection the 
author has aimed at having one, and only one, experi- 
ment in illustration of each principle. 
For example, there is but one general principle in- 
volved in the method of mixtures, whether it be applied 
to the determination of the specific heat of a solid 
or of a liquid, the latent heat of fusion or of vaporisa- 
tion; hence only one laboratory exercise is provided 
in illustration of the method. This extreme pruning 
may sometimes be necessary in an_ introductory 
course, and where circumstances render it necessary 
the plan of the author is no doubt excellent. But we 
feel sure that such an abridgment is not to be desired. 
A student learns so much in finding out the variations 
in a method which are necessary to apply it effectively 
to different purposes that every opportunity for the 
discovery ought to be afforded. 
The description of the selected experiments is 
excellently, if somewhat briefly, made. About half 
the book is devoted to mechanics, which in England 
is usually taken in a separate course. Each chapter 
is concluded with a few problems having considerable 
merit. 
We have only to suggest that in the discussion of 
rotation it should be clearly brought out that the 
moment of the forces must be taken either with re- 
gard to the centre of mass or to an axis fixed in space, 
and further that the moment of inertia is not neces- 
sarily the same in the two cases. 
Ostwald’s Klassiker der exakten Wissenschaften. 
(Leipzig: Wilhelm Engelmann; London: Williams 
and Norgate, 1903.) 
SEVERAL additions to Prof. Ostwald’s important series 
of reprints of classical papers lie before us. We have 
space to do little more than mention the titles of the 
individual volumes, but, in general, we cannot forbear 
expressing pleasure at the increased facilities they 
afford for a student to become familiar with original 
papers connected with the exact sciences. Of course, 
to the English student, translations into English would 
be more acceptable. But, given a sufficient know- 
ledge of German, the handiness of these volumes and 
the valuable annotations of the respective editors are 
sure to prove a great attraction. 
The following are brief particulars :— 
No. 135.—‘‘ Theorie der Gestalt von Flussigkeiten 
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