THURSDAY, DECEMBER 17, 
1903. 
GEIKTE’S GEOLOGY. 
Text-book of Geology. By Sir Archibald Geikie, F.R.S. 
4th Edition, revised and enlarged, 2 vols. Pp. xxi 
+702; ix+705 to 1472. (London: Macmillan and 
Go:, Etd., 1903.) |’ Price 30s. net. 
HEN Sir Charles Lyell found that, owing to the 
rapid progress of geology, his early treatise 
must be extended beyond the limits of one handbook, 
he divided his subject into two parts. In _ the 
““Elements ’’ he described the ancient changes of the 
earth and its inhabitants, as illustrated by geological 
monuments, and in the ‘‘ Principles’? he treated of 
the modern changes of the earth and its inhabitants 
considered as illustrative of geology. In the Elements 
we have a selection of facts upon which geologic 
history is founded; in the Principles we have a state- 
ment of the laws which have governed those changes 
based not only on the records of the past, but also and 
chiefly upon the observation of what is now going on 
in the present. Thus the Principles, which include 
that which we arrive at last, is, as its name implies, 
that which from an educational point of view we take 
first. 
Sir Archibald Geikie has found that, in keeping his 
admirable text-book up to date, he has accumulated 
more material than could be conveniently contained in 
one volume, and has therefore issued it in two; but 
these are two volumes of one work, in fact the break 
takes place in the middle of one of his subdivisions 
of the subject—not inconveniently, however, as the 
first volume ends with the description of the aqueous 
deposits, and the second begins with the igneous rocks, 
both of which are included under structural geology. 
When, however, we look into the work, we see that its 
future is suggested not by its separation into two 
volumes, but by its subdivision into seven books. 
The subject of the first book is the earth’s place in the 
solar system, and the effect of the various cosmical 
forces acting upon it, in producing or modifying the 
geological condition of its crust. These have to be 
taken account of in discussing almost any geological 
question, whether glacial or volcanic phenomena, 
climatal conditions, the distribution of life, the age of 
the earth, or even such a question as the lateral erosion 
of river valleys, which, -as some hold, depends largely 
upon the same influences as those which control the 
direction of the trade winds and ocean currents. The 
Garonne and the Volga, for instance, the one running 
north, the other running south, cling to their right 
bank, owing, it is suggested, to the rotation of the 
earth as they run at an ever increasing or decreasing 
distance from the axis of rotation, Although we must 
allow that this influence is a vera causa, always acting, 
and tending to deflect such running waters east or west, 
still, one cannot but feel that the variations in the level 
of the river beds, the winding of their courses, and the 
earth movements, which are known to/have taken place 
in recent times over the.areas in question, must have 
No. 1781, VOL. 69] 
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been far more important factors in regulating the 
145 
course of the streams. 
In the Second Book we learn about the materials of 
which the earth is composed, the chemical constituents 
of the crust, their mode of aggregation into what are 
known as minerals, and the methods of discrimination 
and classification of the sedimentary and igneous rocks ; 
of rocks in the building up of which living organisms 
have played a part, and of rocks which have been 
altered by mechanical, chemical, or thermal agents 
so much that it is often difficult to recognise what their 
original character was. In this book we have glossaries 
of rock-forming minerals, of rocks of different composi- 
tion and origin, and of various accessory substances, 
many of which are of economic value. 
The author does not propose to treat specially of 
economic questions, but no one can understand the dis- 
tribution and methods of obtaining coal, oil, metals, 
underground waters, and other products of the earth, 
without such a knowledge of their origin and mode of 
occurrence as may be gained from this work. 
The Third Book deals with earthquakes and 
volcanoes, and has to do with the causes of upheaval 
and subsidence, the effects produced by internal heat, 
hydrothermal action, pressure and the accompanying 
chemical and mineralogical changes. These are sub- 
jects to which our author has paid special attention— 
“quorum pars magna fui,’’ he might justly say of 
them—and for this reason as well as from their own 
intrinsic importance, we welcome his fuller treatment 
of them. In the second part of the same book he dis- 
cusses denudation and its correlative deposition, and 
all the various forces of air, water, and ice, and of liv- 
ing things, by which they were brought about. 
The changes which have taken place in the interior 
of the earth we should, at first sight, have thought to 
be one of the last subjects to which experimental 
research could have been applied; yet we learn that 
towards the end of the eighteenth century De Saussure 
set himself to study the possible derivation of rocks, by 
fusing samples of them, and judging whether, as had 
been alleged, some had arisen from the melting of 
others; but Sir James Hall more fully realised how far 
the processes of nature might be imitated by man, and 
about a hundred years ago described a series of in- 
genious experiments, by which he demonstrated the 
possibility of producing either a vitreous or a stony 
condition in fused rocks, according to the rate at which 
they are allowed to cool. Daubrée followed up this 
kind of experimental geology, and showed not only 
that various minerals usually found associated with 
volcanic and metamorphic rocks could be developed 
in the laboratory in their proper crystalline form, but 
also that enclosures and structures, analogous to those 
found in ancient schistose, and altered rocks could be 
artificially produced. 
In Book IV. our author follows up his explanations 
of the modus operandi with an account of the results 
produced, He now describes the arrangement of the 
materials of the earth’s crust, first of all considering 
the sedimentary rocks, their bedding and joints, their 
dip and strike, their cleavage and faults; also the pro- 
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