252 
NATURE 
[JANUARY £4, 1904 
veyed to a sufficient distance, and Mr. Reade points | 
out that, with similarly applied forces, something 
similar should occur in the earth’s crust. 
Results more in accordance with structures noted by 
the geologists are, however, seen in the effects of 
pressure originating in the general expansion of strati- 
fied material. 
An observation bearing upon this form of action, 
which extended over many years, refers to the cumula- 
tive effects of changes produced by hot and cold water 
upon a lead plate forming the lining of a pantry sink. 
First it ridged up to form an overfold and eventually | 
cracked. The fold was cut out, bent down, and 
soldered. In eight years’ time the fold had again 
grown, little by little, by material impercevtibly flow- 
ing to the site of the fold, until it resembled the model 
of a mountain range. 
The crescentic form of this ridge is seen in Fig. 1, | 
the centre of the discs, but one on the right and the 
other on the left of a diameter. By placing cores upon 
the bed plate, or by deforming the bottom dise of clay 
_upon which the other discs are placed, centripetal 
pressure results in anticlinals, spiral folding, various. 
forms of shearing, and other structures, each being 
dependent upon the bias given by the form of the core, 
and it is to multilateral pressures alin to those em- 
ployed in his experiments that the author ascribes 
many of the forms met with in mountain ranges. 
Other interesting chapters relate to the effects of ex- 
pansion due to atmospheric changes in  tempera- 
ture as exhibited by asphalt, cement, rails, and other 
substances, the production of slaty cleavage, and the 
supposed permanence of oceanic basins and conti- 
nental domes. 
The effects of denudation as a factor playing an im- 
portant part in shaping the features of the world are 
Fic. 2.—Photograph of section along saw-cut line a, 4, Fig. 1, showing structure of the fold and overfold. 
(From ‘‘ The Evolution of Earth Structure,"’) 
whilst a section of the same through a, b (Fig. 2) shows 
that it had become an overfold. It 1s a form that could 
not be produced by external pressures, and as it so 
closely accords with the theory it is intended to illus- 
trate, it well deserves the space, which is that of a 
whole chapter, devoted to its history. 
Torsional structures, as, for example, those noted 
in the dolomites, and the curved axes of mountain 
ranges met with in nature, may be explained by multi- 
lateral or circumferential pressure, particularly when 
it is assumed that an initial bias is given by the form 
of the floor on which the strata have been deposited. 
Experimental demonstrations of the effects of this 
form of pressure were made by compressing discs of | 
clay confined by a circular metal loop, the diameter of 
which could be altered, much in the same manner that 
the diameter of a loop in a piece of string may be 
altered by pulling on the two ends. The ordinary effect 
of converging pressure is to produce doming, not in 
NO. 1785, VOL. 69] 
hardly mentioned, the reason being that they have 
already received so much attention from other writers. 
Mr. Reade deals almost entirely with activities which 
are hypogenic, and these, although some of them may 
be old acquaintances, he presents to geologists in a 
manner so novel that they acquire an importance 
which most certainly they did not previously possess. 
The ancient contraction theory is to be largely sup- 
planted by one of expansion and contraction. 
The amount of vertical movement asked for may 
be taken at 10,000 feet, or 1/2000 of the earth’s radius 
—to human beings a quantity that is stupendous, but 
when regarded as a deviation in the smoothness of our 
globe it becomes a quantity that is insignificantly 
small. The author will no doubt find many followers ; 
some may hesitate, but even those who have crystal- 
lised an ancient faith will pause to think and give to 
originality the consideration it deserves. 
J. Mine. 
