OcToBER 12, 1899] 
The treatment of the dynamics of movement as a 
polar change in the resultant of the anabolic and kat- 
abolic processes in the cell, or “ biotonus,” as the author 
calls their algebraical sum, is equally illuminating, as are 
also parts of the mechanics of cell metabolism. 
The pages dealing with actual facts, which after all 
make up by far the greater part of the book, possess an 
enticing feeling of freshness and novelty which is born 
of the fact that the author’s special studies have lain 
out of the beaten track. For this and for the intrinsic 
interest of the facts themselves we feel grateful to him, 
and we heartily wish success to the English edition. 
The translation bears abundant evidence of the care 
which Prof. Lee must have lavished upon it. It is a 
monument of clearness throughout. W. B. Harpy. 
OUR BOOK SHELF. 
Living Pictures. By H. V. Hopwood. Pp. xii+275. 
(London: The Oftician and Photographic Trades 
Review, 1899.) 
THIS is a very interesting review of the gradual evolution 
of the various instruments which have been invented for 
the portrayal of objects in motion, from the earliest times 
to the present day. The work may be divided into two 
parts, of which the first, including Chapters 1.-111. (pp. I- 
109) deals with the more distinctly historical aspect of the 
subject, while the remaining chapters (iv.-vil.) are devoted 
to a very minute description of all the important machines 
in present use. 
Chapters i. and ii., on the ‘“‘ Persistence of Vision,” &c., 
contain a lucid account of the principles governing the 
phenomenon ofa succession of different views of the same 
object giving the impression of the object being in motion. 
In this part all the instruments, whether as toys or scien- 
tific apparatus, are described in the order of their inven- 
tion, beginning with the simple colour tops and thauma- 
trope put forward as early as 1826. The host of im- 
provements from this time up to about 1878 were 
attempts to remedy the difficulty of so small a percentage 
of light passing the two slits at first used for the inter- 
mittent view. This section concludes with descriptions 
of the modern mutoscope and viviscope. 
Chapter iii. (pp. 43-109) commences with the invention 
of “ chronophotography,” and gives a complete descrip- 
tion of the more important of the inventions brought out 
from 1865-1895. The mechanical details in connection 
with the alternate exposure and movement of the sensi- 
tive surface receive special attention, the difficulty of 
following these being greatly lessened by the numerous 
illustrations accompanying the text. 
Chapter iv. is devoted to present-day apparatus, and all 
the machines which have appeared before the public re- 
ceive ample notice, in most cases accompanied by a 
woodcut showing the internal arrangements. 
Chapters v. and vi. deal with the processes adopted in 
making the films, their exposure, development, printing, 
&c., and also give ample practical instructions for 
exhibiting the pictures in the lantern. 
At the end of the volume two most useful appendices 
are given. The first is a “Chronological Digest of 
British Patents,” giving a short vészmé of all specifica- 
tions taken out in connection with living pictures from 
the time of Fox Talbot (1851) to the end of December 
1808. 
The second appendix is an annotated bibliography of 
all publications (British and foreign) from 1825 to the 
present time, which bear on the subject. 
The numerous illustrations (242), which are well chosen 
and very clearly printed, ‘render the following of the 
NO. 1563, VOL. 60] 
NATURE 
567 
necessarily somewhat technical matter exceedingly 
interesting even to the non-expert. The book will be 
welcomed by many to whom the methods of cinemato- 
graphy are a mystery, as by its aid any one even strange 
to the subject may easily understand the working of any 
of the machines in past or present use. 
Tables and Data. By W. W. F. Pullen. 
Scientific Publishing Company, 1899.) 
IN these eighty-seven pages Mr. Pullen brings together 
tables and data which will be found very serviceable in 
engineering laboratory work and in the solution of class 
problems and exercises in mechanical engineering. 
Points perhaps of special mention are that the general 
steam table is carried up to 300 lbs. per square inch ; the 
diagram for determining the dryness of steam with the- 
throttling calorimeter is plotted on a large scale, and the 
melting points of various substances has been revised by’ 
Sir William Roberts-Austen. For facility of reference 
the British and metric measures are placed side by side. 
The remaining portion of the book is devoted to mathe- 
matical notes on mensuration, geometry, trigonometry,, 
&c., with a synopsis of mathematical data. At the end 
are added a few extra pages, some of which are blank, 
while on others are printed diagrams of millimetre paper,. 
for the insertion of any additional curves the student may 
wish to insert. Not only engineering students, but others 
should find the contents of this book a useful laboratory 
vade-mecum. 
(Manchester : 
LETTERS TO THE EDITOR. 
The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NATURE. 
No notice zs taken of anonymous communications. | 
Halo Round a Shadow. 
IN your issue of this week Prof. S. Newcomb draws attention 
to the halo which an observer often sees round the shadow of 
his own head when the ground on which the shadow falls is 
covered with vegetation or any obstructions which can them- 
selves cast shadows. 
In a letter to NATURE in 1878 or 1879 (I have not the 
reference by me) I mentioned this phenomenon, giving the: 
same explanation as your recent correspondent, and adding that 
the angular width of the halo was settled by the ratio of the 
mean diameter of the obstructions to their distance from their 
own shadows. 
The halo (or spot of light, if the observer is too far off for his 
own shadow to show) can be seen very well when the ground is 
covered with heather or bracken whose twigs and leaves are 
small compared to their height above the ground. 
3 Victoria Street, S.W., October 6. A. MALLOCK. 
The Skull of Hatteria. 
Ir may be worth while to draw the attention of naturalists to 
an omission in the figures of the skull of that archaic reptile, the 
Tuatara, that occur in two recent text-books of somewhat wide 
circulation, viz. Parker and Haswell’s ‘‘ Text-Book of Zoology” 
and Reynolds’s ‘‘The Vertebrate Skeleton.” These figures 
are either copied or redrawn from Zittel’s figure published in 
his well-known work on Paleontology. This figure appears to 
have been drawn from an imperfect specimen, as the ‘‘trans- 
verse” (or transpalatine) bone is omitted in the ventral view ; 
it is afparently represented in the dorsal view, however, though 
there isno index line in the original, The bone, though of 
considerable size, very readily drops out of a thoroughly 
macerated skull, from which the figure was no doubt drawn. 
There is really no excuse for our English authors borrowing the 
figure from a German book in this instance, for Dr. Giinther’s. 
picture of the skull published in the Phz/, Trans. vol. clxvii.,. 
is perfectly accurate, except in regard to nomenclature of some: 
of the bones, while Zittel’s is most indistinct. 
Dunedin, N.Z., August 30. W. BLAXLAND BENHAM. 
