Supplement to “ Nature,” March 14, 1907 
Vii 
to a stranger presents itself as a very uneven treat- 
ment of the subject. 
While lenses have eighty-nine pages devoted to 
them, more than a third of the volume, all the various 
methods of silver printing are dismissed in but forty- 
four lines. We find that toning silver prints has 
fourteen lines devoted to it, platinum printing twenty- 
two lines and two equations, while the use of spoiled 
lantern plates by cleaning off the films and utilising 
the glass compares with the above important subjects 
with its twenty-nine lines. The incompleteness of the 
consideration of some other subjects, such as halation 
and intensification, leads sometimes to statements 
that may convey a false impression. We read, for 
example, that by continuing the development of an 
exposed gelatino-bromide plate ‘‘ the image will gain 
steadily in density until all the silver present has been 
reduced, when of course the process ends ’’—a state- 
ment that even mere rule-of-thumb photographers 
know, often to their cost, is not true. Here, as in 
one or two other cases, theoretical considerations 
seem to have misled the author with regard to facts. 
In short, he does not seem at home in the treatment 
of what might be cailed the more strictly photographic 
parts of the subject. 
It is easy to discover the sections of the subject 
that the author delights in, and it is in these that 
the value of the book consists. The chapters on 
lenses do not go deeply into the matter, but they are 
interesting and clear, and give those details that 
students want. The representations of the light re- 
flected from the glass-air surfaces of single, doublet, 
and triplet lenses, and a lens with four separate 
glasses, are novel as book illustrations and very in- 
structive. In the directions given for testing a lens 
for its defining power, the fact that commercial] 
plates are not flat is very properly emphasised, but 
this fact is overlooked in the method given for test 
ing a camera for ‘‘register.’’ It is to be regretted 
that depth of definition is treated of in the orthodox 
manner, namely, only as it affects that part of the 
plate immediately adjacent to the lens axis. In 
direct contrast to this, the author does not follow in 
the footsteps of most of his predecessors with regard 
to illumination, considering the effects of focal length 
and aperture only, but demonstrates exactly how the 
brightness of the image on the plate must fall off 
at a distance from the lens axis under even the best 
experimental conditions. 
The chapter on exposure shutters shows that the 
author is practically familiar with them. He gives 
the main facts concerning them, and the methods that 
he has used himself in investigating their mode of 
action. He gives a table, two and a half pages in 
length, of the distances that a body falls in each 
hundredth of a second for a distance fallen of from 
2 feet to 20 feet. This ponderous method of timing 
shutters is surely obsolete. The rotating bicycle- 
wheel method is also described, as well as methods 
of investigating efficiency. 
Photomicrographs of the grain of plates that have 
been subjected to various treatments are a notable 
feature of the work. Cee 
NC, 1950, VOL. 75] 
THE FAUNA OF THE TAY DISTRICT. 
A Fauna of the Tay Basin and Strathmore. By J. A. 
Harvie-Brown. Pp. Ixxxvi+377; plates and maps. 
(Edinburgh: D. Douglas, 1906.) Price 30s. 
V ITH the appearance of this handsome worl the 
author has the satisfaction of having completed 
the tenth volume of ‘‘A Vertebrate Fauna of Scot- 
land”: and we have great pleasure in congratulating 
him on having progressed thus far with a task stu- 
pendous enough to have frightened any man from 
attempting. Not that Mr. Harvie-Brown has written 
the whole, or anything like the whole, of the preceding 
nine volumes. On the contrary, he was associated 
at the commencement of his work with the late Mr. 
T. E. Buckley, who contributed largely to several of 
the volumes; while the second volume—on the birds 
of Iona and Mull—was written by the late Mr. H. D. 
Graham, and the late Mr. H. A. Macpherson was 
joint-author (with the editor in chief) of the one on 
the fauna of the North-west Highlands and Skye. 
The volume on Shetland is, again, the work of 
Messrs. Evans and Buckley. Nevertheless, the burden 
of the work as a whole has been borne by Mr. Harvie- 
Brown, and if he live to complete his task the author 
of the present volume will have accomplished for the 
whole of Scotland what his coadjutor Macpherson did 
for ‘‘ Lakeland’’; and this, too, in a style which few 
can equal and none surpass. For Mr. Harvie-Brown 
is not only an exceedingly careful and industrious 
investigator, who will never let go a trail until he has 
hunted it to the end, and will never rest satisfied until 
he has completely refuted a doubtful assertion, but 
also a writer gifted with the power of putting facts 
in a pleasant light and of interesting his readers (who 
we hope are many) from start to finish. He is, in 
fact, both an accomplished and elegant writer and an 
enthusiastic and painstaking field-naturalist—a com- 
bination which can scarcely fail to produce attractive 
and trustworthy work, as it has done in the volume 
now before us. 
As to the importance of works of this nature—more 
especially to those who come after us—no words of 
ours are necessary. With the exception of one of a 
dotterel on her nest by Mr. C. Kearton, and of a 
second of the Perthshire Museum, the illustrations in 
the present volume are by Mr. W. Norrie; and when 
this has been stated, any commendation would be 
superfluous. 
In two respects the author has been specially 
favoured by adventitious circumstances in the case of 
the present volume. In the first place, the area of 
which he treats lies in the heart of that great bay 
on the east coast into which the estuaries of the Tay 
and the Forth discharge, and it is consequently one 
peculiarly favourable for the arrival of birds migrating 
or driven from the eastward. That such is really 
the case is evident by a glance at the map of the 
spread of the little auk over Scotland, facing p. Ixxxxv. 
In the second place, Perthshire possesses a number of 
local observers specially interested in the fauna of 
the district; and likewise a museum entirely devoted 
(as it should be) to the illustration of the local natural 
history. As examples of the richness of the avifauna 
