98 
great as to lead to the general adoption (by continental 
makers) of small circles with powerful reading micro- 
meters in place of large circles with verniers. 
A very simple process of making relief maps in Germany 
is described, viz. by cutting out contour strips from a con- 
toured map, and pasting each on to cardboard cut to 
same outline. Altogether the Report is a very interesting 
one. ALLAN CUNNINGHAM 
GREEN’S “GEOLOGY” 
Geology. By A. H. Green. Part I. Physical Geology. 
Third and Enlarged Edition. (London: Rivingtons, 
1882.) 
— TUDENTS of Geology will welcome this third and 
- much enlarged edition of Prof. Green's excellent 
text-book, though they may at first sight regret the 
exchange of the old convenient manual form of the book 
for that of the present handsome and well-printed octavo. 
One of the first features that strikes the reader in this 
new issue of the work is the large augmentations made 
to the lithological sections. In fact this part of the 
treatise may be said to have been re-cast and almost 
wholly re-written. The author devotes 150 closely printed 
pages to crystallography and the description of minerals. 
It may be open to question whether the full details which 
he gives to the crystallographic characters of minerals are 
not rather out of place in a geological treatise. They are 
not ample enough for the mineralogical student, and the 
geologist who takes up the subject must necessarily study 
text-books of mineralogy, where they are given at much 
greater length. Prof. Green, however, has put them so 
clearly and succinctly that this portion of his book cannot 
fail to be of use. 
Some changes have been made in the arrangement of 
rocks. The non-crystalline or derivative rocks now come 
first—a grouping which no doubt has its advantages in 
teaching, particularly in elementary classes, but which is 
not that usually employed in petrographical works After 
briefly describing the lithological character of the non- 
crystalline rocks, the author, following his original plan, 
proceeds to discuss the mode of formation of these rocks, 
dealing first with denuding agents and their work, and 
then considering the manner in which the denuded mate- 
rial is aggregated into rock-masses. In these sections he 
brings his subject abreast of the onward march of the 
science. Another change in the original treatment of his 
subject occurs in the author’s chapter on the “‘ confusedly 
crystalline rocks.’’ He has not been so happy in his 
choice of a title for them as he has been in his descrip- 
tion of their general characters. After giving an account 
of the lithological features he proceeds to discuss their 
modes of origin, dealing first with volcanoes recent and 
extinct, then with earthquakes (though one wonders what 
these have to do with a description of crystalline rocks), 
next with plutonic rocks which, however, are rather in- 
adequately discussed. The chapter on metamorphic 
rocks has been carefully revised,'and may be commended 
to the student as an admirable summary of what is at 
present known on this subject. The chapter upon the way 
in which rocks came into their present positions was one 
of the best in the first edition of the book. Its excellence 
has now been increased by a thorough revision. For 
NATURE 
[Mov. 30, 1882 
practical insight into the structure of the earth’s crust it 
is unsurpassed in any treatise known to us. 
Prof. Green more than makes up for the curious omis- 
sion in the first edition of any mention of mineral veins. 
We doubt, however, the advantage of inserting minute 
descriptions of metallic ores in a general geological text- 
book. The author would do well in his next edition to 
give references to the Continental works on mining, par- 
ticularly to some of the numerous treatises which have 
been published in Germany. Chapter XIII. retains its 
place as a valuable account of how the present surface of 
the ground has been produced. The last two chapters 
discuss the former fluidity and present condition of the 
earth’s interior, the cause of upheaval, contortion, and 
metamorphism, and the origin of the changes of climate 
which have taken place during geological time. These 
parts of the book are exceedingly well done. The author 
has held the balance fairly between contending disputants, 
and sums up the evidence with conspicuous and judicial 
impartiality. Altogether, he may be congratulated on the 
appearance of this edition of his text-book, which sustains 
and extends his reputation as an exponent of his favourite 
science. 
OUR BOOK SHELF 
A History of British Birds. By the late William Yarrell. 
Fourth Edition, Revised to the end of the Wryneck, by 
Alfred Newton, M.A., F.R.S., continued by Howard 
Saunders, F.L.S., F.Z.S. Part XV. (London: John 
Van Voorst, November, 1882.) 
THE fifteenth part of the new edition of what the 
British ornithologist fondly calls his ‘ Yarrell” con- 
tains the final contribution of Prof. Newton to this 
work, and the first pages of the portion which Mr. 
Howard Saunders, his successor in the editorship, has 
undertaken. Few of the subscribers, we believe, will be 
much pleased with the change of authorship of their 
favourite work of reference. No living writer, it may be 
confidently asserted, is so competent to prepare a new 
edition of “ Yarrell’s British Birds’’ as Prof. Newton, 
and the conscientious care with which he has laboured 
upon the two volumes now completed must be patent to 
all who consult them. At the same time it should not be 
forgotten that time is an element in all human matters 
not even excepting books on British birds. When, there- 
fore it is considered that nearly eleven years have elapsed 
since Prof. Newton commenced his new edition, and that 
only the first half of the work is now completed, it is 
obvious that the Professor has not acted unwisely in sur- 
rendering the second half to an editor who is able to 
devote more time to the undertaking. 
Mr. Howard Saunders, it is generally understood, 
intends to issue the two final volumes of the new edition 
in two years, and if his health and strength permit, will 
doubtless accomplish his task within the allotted period. 
In this his large practical knowledge of the bird-life of 
Southern Europe, as well as his well-known familiarity 
with modern ornithological literature, are likely to be of 
the greatest assistance. 
Mr. Saunders commences his second volume with the 
pigeons, and gives us an excellent account of the four 
British species, as also of the American passenger pigeon, 
which can only be looked upon as one of our rarest 
stragglers from the New World. When, however, he 
says that all true pigeons lay two eggs he must have for- 
gotten that the crowned pigeons, and the numerous forms 
of fruit-pigeons are, so far as is known, content to lay but 
one. There is therefore no good reason for calling the 
