218 NATURE 
[JANUARY 3, 1907 
charge. One might go so far as to suggest that it 
is only by accident that a character developed at one 
period in the life-history becomes of use at another, 
for such utility almost always involves a change of 
primitive function that could not have been foreseen 
at the first appearance of the structure in question. 
Thus to quote the case of the floating mechanism, the 
stimulus that provokes the formation of air-filled 
spaces is most often connected with respiration, and 
they are first ‘“‘adapted’’ for this purpose. Their 
subsequent use for floatation is an accident. It is 
true it may be of immense importance to the species, 
but its value could not, so to say, have been foreseen 
by the individual in which it arises. 
A chapter on mangroves forms an interesting diver- 
sion from the main track of the thesis. It is 
known that curious barren forms of the genus Rhizo- 
phora occur in various regions. These apparently 
combine the characters of more than one species, but 
the suggestion is put forward that they are not 
hybrids, but represent examples of dimorphism. 
The hypothesis is rather startling, but it is very well 
worth while testing. If it should prove to be well- 
founded, the investigation would certainly yield re- 
sults of considerable scientific importance. 
Limitations of space preclude the possibility of 
attempting to discuss the great bulk of new and 
interesting observations that crowd the pages of Mr. 
Guppy’s book, but enough has been said to show 
that the author has made a very real contribution to 
biological science. Ife 18h. 8 
PETROLEUM AND ITS PRODUCTS. 
Petroleum and its Products. By Sir Boverton Red- 
wood. Two vols. Pp. xxxii+ 1064. Second 
edition, thoroughly revised and enlarged. (London : 
Charles Griffin and Co. pletd)i Pricesags) net: 
O harder task exists than to criticise a book with 
which the reviewer is in complete accord, and 
so perfect an example of what a book of reference 
should be as Sir Boverton Redwood’s monograph on 
petroleum and its products, of which the second 
edition has now been issued, offers no mark for 
criticism. 
The ten years which have elapsed since the first 
edition of this work was published have seen many 
advances in the industrial use of petroleum products, 
and a period which has been marked by the growth 
of the use of liquid fuel from the experimental stage 
to the important position it now occupies in the 
principal navies of the world, and the perfection of 
the internal combustion engine with its widespread 
application, has brought in its wake so many altera- 
tions and modifications in processes that a complete 
revision, and indeed re-writing, of a very large portion 
of the book has been necessitated, the two volumes 
now containing more than a thousand pages. 
The first section of the work deals with the history 
of the petroleum industry, from the use of bitumen 
in building the Tower of Babel down to statistics as 
recent as 1904, and this portion of the work is ren- 
dered the more valuable by the data being subdivided 
NO. 1940, VOL. 75] 
under the headings of the various countries in which 
petroleum is found. [ 
The geological and geographical distribution of 
petroleum and natural gas occupies the second section, 
which is illustrated by maps of the principal oil- 
bearing districts, and cross sections of some of the 
more important oil fields and wells. A consideration 
of the oil fields of the world naturally leads to the 
discussion of the chemical and physical properties of 
petroleum and natural gas, which occupies the third 
section of the worl, and contains a wonderfully com- 
plete compilation of the enormous amount of work 
which has been done on the subject, and which is 
rendered the more valuable by the BOIEGRCES being 
given for all the works quoted. 
The next section deals with the much-vexed ques- 
tion of the origin of petroleum and natural gas, and ‘ 
a discussion of the various theories which have been 
from time to time formulated, and although the 
balance of evidence is distinctly in favour of the views 
expressed by Héfer and Engler, as to petroleum being 
of animal origin, whilst natural gas is a secondary 
product of the same decomposition, the reader cannot 
help the conviction that there are many cases in which 
a vegetable or even inorganic origin might have 
caused the deposits. ; 
The fifth section will be considered by many readers 
one of the most important in the work, dealing 
as it does with the methods adopted for winning the 
crude oil, and much of the practical information as 
to the methods employed in the American, Canadian, 
Russian, and other oil fields is founded on the author’s 
own experience. 
The important subject of refining the oil, which 
occupies the next section, covers not only the general 
methods employed, but also the details of the methods 
of manufacture adopted in America, Russia, and else- 
where, and is enriched by numerous references and 
extracts from the work of Engler and other Conti- 
nental authorities too little known in England. 
The shale oil industry, being of British origin, 
claims a large amount of interest, and the struggles 
of James Young in founding it on its present basis 
form a fitting introduction to the seventh section, 
dealing with shale oil and allied industries, whilst 
an able section on the transport, storage, and distri- 
bution of petroleum ends the first volume of the book. 
To the chemist the second volume is even more 
interesting than the first, as the reader is at once 
plunged into the methods adopted for the testing of 
crude petroleum and the many products obtained from. 
it, and especially interesting is the historical account 
of the early legislation with regard to the flash point, 
and the part played by Sir Frederick Abel and the: 
author in fixing the flash point at its present value. 
This section also contains a full account of the beauti-. 
ful method of testing for petrol vapour and other 
inflammable vapours in air devised by Prof. Clowes. 
and the author, which depends on the fact that a 
hydrogen flame of fixed dimensions burning in air 
containing a small proportion of inflammable gas or 
vapour is seen to be surmounted by a small cap or- 
halo, the size of which indicates the amount of in~ 
