June 3, 1915] 
NATURE 367 

twenty-one chapters, and deal with the class of 
explosives that may be called ‘‘ propellants.’’ In 
reading them two criticisms arise—the first being 
that the subject matter is so subdivided as to 
destroy continuity, and the second is that a vast 
amount of detail as to manufacture and history of 
the explosives has been presented to the reader 
without any attempts being made to give an idea 
of the principles on which the composition and 
action of explosives depend. The explanation of 
this is probably to be found in the statement made 
in the preface that ‘‘ subjects which are treated 
fully in the ordinary scientific or technical text- 
books have only been dealt with in so far as they 
throw new light on problems connected with 
explosives.”’ 
This limits the utility of the book, as although 
a collection of widely scattered results from many 
sources is a great help to the workers in the 
subject, the addition of a chapter in the early 
part of the book, dealing with the principles on 
which the subject rests, would have enormously ex- 
tended the public to which the work would appeal. 
The next portion of the book deals with blasting 
explosives, and in Part vill, we come to the 
properties of explosives, such as their physical 
character, the pressure and heat, power and vio- 
lence of explosion, and a chapter on ignition and 
detonation. 
Part ix. is devoted to special explosives, such 
as fuses, safety explosives and fireworks. The 
chapter on safety explosives gives an interesting 
account of the testing galleries to be found in the 
mining centres of various countries, and the pro- 
cedure adopted for testing the liability of explo- 
sives to ignite mixtures of coal gas or methane 
and air, and also coal dust suspended in air. The 
whole chapter is so well done that it is a pity 
that the author does not point out more strongly 
that the class of explosives to which 
methods of testing have given rise are safe 
in name only, as those in which nitroglycerin 
is the explosive basis are so diluted with car- 
bonaceous matter as to give on _ explosion 
volumes of carbon monoxide, a poisonous and in- 
flammable gas, whilst the ammonium nitrate class 
often contains so large an excess of this salt, used 
in admixture with trinitrotoluene or other ex- 
plosive body as to give an excess of oxygen, 
which must always be a danger in a coal bore. 
Part x. deals with stability, whilst in Part xi. 
materials and their analysis are fully discussed. 
Throughout the thirty-six chapters in which the 
book is divided full references are given to the 
original memoirs from which quotations are made, 
whilst there is an appendix and an index of names 
as well as of subjects. 
NO. 2379, VOL. 95] 
these 

FEEBLE-MINDEDNESS. 
Feeble-mindedness: its Causes and Consequences. 
By Dr. H. H. Goddard. Pp. xii+599. (New 
York: The Macmillan Co. ; London: Macmillan 
and) €o:, Lid., 1914.) Price 17s. net. 
HIS is the most recent American work deal- 
ing in authoritative and _ scientific 
manner with what is now known in this country 
as mental deficiency. Some years ago Binet and 
Simon devised a method of classifying mentally 
defectives according to the degree of intelligence 
they had attained, comparing the results of certain 
tests with those obtained from normal children 
of various ages. Thus, mentality 4 means that 
the patient has attained the intelligence of a child 
aged four years. This classification is adopted 
throughout the present work, certain general 
terms being used in accordance with the Ameri- 
can general classification on the same _ basis. 
Patients of mentality 1 or 2 are called idiots, 
those of mentalities 3 to 7 are called imbeciles, 
and those from 7 to 12 are called morons. 
In some preliminary remarks respecting the 
relationship of feeble-mindedness to certain other 
social evils, the author quotes statistics or com- 
an 
petent opinions which seem to show that at least 
50 per cent. of criminals, prostitutes and paupers 
(inmates of almshouses), many ne’er-do-wells and 
some alcoholics are feeble-minded. It is also men- 
tioned that So per cent. of truants are feeble- 
minded, the explanation being that truancy is the 
result, and not the cause, of failure in school- 
work. 
The greater part of the book is devoted to the 
study of heredity in relation to feeble-mindedness. 
This investigation is so thorough that it com- 
prises the labours of a whole field of trained in- 
vestigators, for it is clear that no one man could 
carry out by himself the enormous amount of 
work recorded in Dr. Goddard’s book. Not only 
is a detailed family history obtained, but as many 
members of the family as possible are personally 
seen and examined or, when this is not possible, 
inquiries are made of the inhabitants of the 
village where the person lived respecting his in- 
tellectual capacity. In this way a history is ob- 
tained of every individual member of the family 
tree for three, four, five or, in one case, six genera- 
tions back. When we reflect how few of us 
could give particulars of so many of our ances- 
tors, we can appreciate the amount of labour 
which has been expended in this field. 
In chapter v. the author collects the data of his 
charts in a series of twenty-one tables and shows 
the etiological influence, positive or negative, of 
alcoholism; paralytic, epileptic, insane or syphi- 
litic parentage or affection; tuberculosis; sexual 
