JANUARY 14, 1904] 
NATURE ; 
5! 
EARTH STRUCTURE.' 
pS a copiously illustrated volume Mr. T. Mellard 
Reade, the well-known author of the ‘‘ Origin of 
Mountain Ranges,’’ expounds his views on certain 
geomorphological changes of profound interest to geo- 
logists. By tumefaction, wrinkling and denudation, 
the features of the face of our world are ever changing. 
Evidences of the former activity by which regions 
of vast extent have been elevated or depressed almost 
vertically are, for example, found in raised sea beaches 
and submerged valleys. Fossiliferous rocks high up 
in mountain ranges, as in the Alps and Himalayas, 
attained their present positions by wrinkling during 
the process of mountain building. 
Sedimentation results in the filling up of depressions, 
but its weight, no matter how mobile the undercrust 
may be, is not, according to the author, sufficient to 
raise neighbouring areas. Also it must not be over- 
looked that the phenomena presented 
to us represent pulsatory movements 
by which large tracts have been 
alternately raised and- lowered. 
Secular contraction, inasmuch as it 
acts in one direction, does not seem 
adequate to explain these regional 
breathings. If by this and other 
well-known hypotheses we fail to ex- 
plain vertical elevations and de- 
pressions, Mr. Reade invites us to 
consider the following. 
We live on a rocky crust some 
thirty miles in thickness which rests 
upon a shell of igneous magma. By 
the expansion or contraction of 
portions of this magma due to 
changes in its temperature, tracts of 
the superincumbent crust are raised 
or lowered. The first question we 
are inclined to put relates to the 
manner in which these assumed 
variations in temperature are 
brought about. Blanketing by de- 
position of sediments the author re- 
gards as insufficient, but that there 
are such local subterranean alter- 
ations in temperature is evidenced by 
the shifting of volcanic centres and 
the intermittent activities of the 
same. 
Variations in the character of 
lavas which have issued from the 
same vents, but at different times, 
indicate chemical and mechanical 
changes in a subjacent magma, and 
with such changes heat may be 
evolved or absorbed, and a magma 
may increase or decrease in its volume. Attention is 
also directed to the remarkable chemical and 
mineralogical alterations and the accompanying volu- 
metric changes which have taken place in rock masses. 
With the phenomena of recalescence and magnetisa- 
Fic. 
tion, alterations in bulk take place. In short, 
- 2 : . 6 
“the earth is not an inert mass cooling in space,”’ 
but it is a planet within which there is flux 
and reflux, action and reaction, mechanical, chemical, 
and other activities in operation which result in 
the evolution of heat and alterations in volume, and 
in the latter we are to loolx for the cause of vertical 
elevations and depressions. References to the effect 
of these displacements in altering the level of oceanic 
water are made. The swelling or contraction of a 
1 “The Evolution of Earth Structure, with a Theory of Geomorphic 
Changes.” By T. Mellard Reade. Pp. xvy+342. (London: Longmans 
and Co., 1903.) Price 21s. net. F 
NO. 1785, VOL. 69 | 
forming the jining of a pantry sink. 
** The Evolution of Earth Structure.’’) 
magma beneath an ocean bed must result in a general 
rise or fall of water on the land. i 
The second form of geomorphic change considered 
is that which is due to a tangential creep and ridging of 
sediments due to fluctuating increases in temperature, 
and consequent expansion brought about by sediment- 
ation. The wrinkles or mountain ranges on the face 
of the world are the results of such changes. With 
a falling temperature contraction sets in, strata 
shorten, and tensions result in faulting. By the fault- 
ing, wedge-shaped blocks fall inwards to act like key- 
stones for the material on their flanks. The old theory 
that the features of the world are largely due to a shell 
accommodating itself to a retreating nucleus also 
accounts for the formation of the wrinkles by com- 
pression, but, unlike the theory advocated by Mr. 
Reade, it does not provide an explanation for normal 
faults which partition the roof of the world into block- 
t.—Showing cumulative effects of chanzes produced by hot and cold water upona lead plate 
A section along a, 4, is shown in Fig. 2, (From 
like masses. That continental outlines are due to sub- 
sidences of the neighbouring oceanic basins, and are 
therefore sketched out by fault lines, is, according to 
the author, very doubtful; at all events, evidences of 
such dislocations, we are told, remain to be discovered. 
His own view is that for the most part such outlines 
are defined by mountain ranges, which represent thick 
accumulations of detritus derived from the denudation 
of land areas, lifted up by expansion on the platforms 
where they were deposited. 
A large section of the work refers to observations 
and experiments which throw light upon the foregoing 
hypotheses. The effects of end pressures as applied 
to layers of sheet lead, bars of soap, damp sand, and 
other materials are already fairly well known. An 
anticlinal rises near to the source of pressure, but the 
foldings are not altogether in accordance with those 
observed in nature. The effects of thrust are not con- 
