Marcu 31, 1923] 



































It is much to be deplored that such a cumbersome 
sentence-like name as “ Echinofossulocactus ” should 
have been brought into use, but unfortunately there 
seems no valid reason for its rejection, for although it 
has been overlooked, it was proposed and characterised 
Sr years ago. It would, however, be of benefit to 
horticulturists and botanists alike, if, at the next 
Botanical Congress, a law could be made to prohibit 
the formation of such atrocious names in future. 
_ The charming coloured plates give a good idea of the 
beauty of the flowers of these prickly plants, and the 
showing some of them as they grow wild will 
convey to the mind of the cultivator the appearance 
ey should have when well cultivated. Of the 
plants figured, Ferocactus rectispinus is one of the most 
triking on account of the formidable aspect it presents 
y its stout straight spines about 4 inches long. Of all 
he flowers figured the most remarkable is that of 
Denmosa rhodacantha (better known as Echinopsis 
acantha), which is curved in a sigmoid manner, 
ind has the petals closed tightly around the exserted 
stamens and style, quite unlike that of any other 
genus. 
The well-known spineless Echinocactus Williamsii 
is rightly removed from that genus and now forms a 
nonotypic genus under the name of Lophophora 
Villiamsii. This plant has remarkable narcotic pro- 
perties and has long been used by certain tribes of North 
American Indians in some of their ceremonies. One 
peculiarity of this plant is that its stamens are irritable, 
and when touched at the basal part they rapidly close 
in around the style, dusting their pollen upon the insect 
or other thing that touched them ; an evident means of 
securing cross-fertilisation. A very full index com- 
letes the volume. There remain to complete the 
york the subtribes to which the genera Mammillaria 
and Rhipsalis belong. N. E. Brown. 

Our Bookshelf. 
Kinematograph Studio Technique. (Technical Primers.) 
By L. C. Macbean. Pp. xii+111. (London: Sir 
Isaac Pitman and Sons, Ltd., 1922.) 2s. 6d. net. 
AccorDING to the subtitle of this little book, it is “a 
practical outline of the artistic and technical work 
in the production of film plays for producers, camera- 
men, artistes, and others engaged in or desirous of 
entering the kinematograph industry.” There are 
hapters on production, the camera and its lenses, 
Studio lighting and outdoor work, dark-room pro- 
cedure, and so on. No previous knowledge of the 
subject is assumed, and many will be interested to 
learn of the artifices by which some of the more striking 
film scenes are produced, while they may also be 
Surprised at the amount of painstaking labour and 
attention to detail which goes to the making of a 
successful film. 
NO. 2787, VOL. 111] 
NATURE 
427 
The Chemistry of Dental Materials. By Prof. C. S. 
Gibson. Pp. 176. (London: Benn Bros., Ltd., 
1922.) 12s. 6d. net. 
A CAREFULLY selected area in chemistry, largely metal- 
lurgy, is dealt with in this treatise, but what is done 
appears thorough. The treatment is not narrow and 
utilitarian, but as scientific as is possible. The second 
half of the book deals with miscellaneous materials 
used in dentistry, such as porcelain, cements, abrasive 
materials and antiseptics, and in this, of course, much 
information is given which cannot be found in the 
ordinary text-books of chemistry. The Brunner-Mond 
process for zinc, described on p. 100, is said to be now 
obsolete, and the same applies to the third form of tin 
(p. 105). Some mention of modern processes for lead 
extraction might have been given. Davy’s name is 
incorrectly given on p. 146. 

(x) Installations électriques industrielles: Installation 
‘—Entretien—Contréle. Par R. Cabaud. (Biblio- 
théque Professionnelle.) Pp. 333. (Paris: J. B. 
Bailliére et fils, 1922.) 10 francs net. 
(2) Alternating Current Electrical Engineering. By 
P. Kemp. Second edition. Pp. xi+5r15. (London: 
Macmillan and Co., Ltd., 1922.) 17s. net. 
(x) Tue first part of M. Cabaud’s book deals in a general 
way with electric installations for light and power. The 
numerical examples given will be helpful to the practical 
engineer. The maintenance of an installation is dis- 
cussed in the second part, and in the third part methods 
of control are described. Various methods of penalis- 
ing consumers who take their supply at a low-power 
factor are given. 
(2) The principal changes in the new edition of Mr. 
Kemp’s book are a new chapter on the protection of 
alternating current systems, and a number of altera- 
tions in the chapters on instruments. 
The Radio Amateur’s Hand Book. By A.F. Collins. Pp. 
xix + 329 +8 plates. (London, Calcutta, and Sydney : 
G. G. Harrap and Co., Ltd., 1922.) 7s. 6d. net. 
A PoPuLAR description of radio communication which 
will be helpful to amateurs is given in this book. The 
author uses the proper technical terms, so any one who 
has read this book will be in a position to benefit 
by more advanced treatises on the subject. In the 
glossary, however, the attempt to define highly tech- 
nical terms in the simplest language is of doubtful 
utility. Capacity is defined as “any object that will 
retain a charge of electricity.” The book concludes 
with a long list of radio “ don’ts,” which will prove 
instructive to the beginner. 
The Pupils’ Class-book of Geography: the Americas. 
By Ed. J. S. Lay. Pp. 176. (London: Macmillan 
and Co., Ltd., 1922.) 15. 3d. 
Ir is not easy to write an elementary text-book on 
geography which has any interest for the pupils who 
use it and at the same time is truly geographical, 
but Mr. Lay appears to have succeeded. His book is 
accurate, readable, and well illustrated by excellent 
black and white maps, and presents the essential 
features of the geography of the Americas. 
