August 26, 1922] 



NA TURE 



271 



contents may be summarised as follows. The first 

 chapter deals with some theories of world formation, 

 Laplace's nebular hypothesis being a special object 

 of attack. The second chapter discusses the nature 

 of the earth's interior, after which four chapters relate 

 to the facts and problems connected with volcanic 

 lava. A broader viewpoint is returned to in chapter 7, 

 which treats of the changes of figure through which 

 the earth has passed ; this subject is further developed 

 in the following five chapters, the titles of which refer 

 to the present regions of rapid change, the contrasted 

 aspects of the earth's face, the migrational movements 

 of the earth's surface, the patterns of the " facial 

 wrinkles," and the design of the fracture marquetry. 

 The bearing of the composition of lavas on the question 

 of earth physiognomy is then dealt with, and the final 

 (fourteenth) chapter again reviews the theories of the 

 earth. The author gives a list of references at the 

 end of each chapter to works and papers on the sub- 

 ject of the chapter, but no general index of names or 

 subjects is provided, an omission which should be 

 supplied if a second edition is called for. 



Despite the somewhat terrifying vocabulary of the 

 geologist, the book contrives to be interesting, and 

 one of its most commendable features is its wealth 

 of illustration, by diagrams, maps, and photographs. 

 The discussion is of a less broad and comprehensive 

 character than the title would lead one to expect, the 

 balance of the book being rather upset by the promin- 

 ence given to the vulcanological topics in which the 

 author is specially interested. In themselves, how- 

 ever, these chapters contain some of the most novel 

 and interesting parts of the book. 



A more serious criticism than that of the title is 

 that the author makes no mention of much important 

 recent work bearing on his subject, as, for example, 

 when dealing with general theories of earth formation, 

 where one is surprised to find nothing about Jeans's 

 cosmogonic researches. The author is particularly 

 concerned to overthrow the notion, based on observa- 

 tions of volcanic lava, that the earth's interior is 

 molten, only the crust being solid. This view has been 

 generally abandoned by geophysicists, on the ground 

 of seismological and other evidence which the author 

 describes. It has, however, long been historically 

 connected with Laplace's nebular hypothesis, though 

 the latter is of much later date, and the two theories 

 are not necessarily bound up together. 



The author gives much prominence to Chamberlin's 

 arguments against Laplace's theory, and regards them 

 as destroying the last support of the hypothesis of a 

 molten interior, and as necessitating a fundamental 

 revision of geological theories. Nevertheless, strong 

 as are Chamberlin's arguments — based on considera- 

 NO. 2756, VOL. 1 lo] 



tions of angular momentum — they have not convinced 

 so great an authority on cosmogony as Jeans that 

 Laplace's nebular theory must be finally condemned, 

 though Jeans has propounded a modified form of the 

 theory to explain the origin of the solar system, which 

 is of a very special type among celestial objects ; in 

 this theory the planets are supposed to have been 

 separated from the sun, when the latter was much 

 more diffused than now, by the passage of another 

 star at a distance comparable with the sun's diameter 

 at the time. This theory thus preserves the feature 

 of Laplace's hypothesis which seems specially in dis- 

 favour with the author, viz. that the earth has cooled 

 down from a diffuse gaseous state. The author him- 

 self advocates the planetesimal hypothesis, i.e. that 

 the earth originated as a solid body by the aggregation 

 of meteoritic material. However great the claims of 

 this view may be regarded, our present knowledge, or 

 rather ignorance, of the effect of pressure upon hot 

 bodies certainly does not permit us to preclude the 

 other view, that the interior of a large gaseous body 

 might become solid under the influence of the pressure 

 of the upper layers, before or at the same time as the 

 formation of a solid crust. 



Another outstanding omission to refer to recent 

 work bearing on the subject relates to Wegener's 

 theory of moving continental masses, now so much 

 discussed by continental geologists. By many in- 

 teresting diagrams the author shows the situation of 

 the regions of present rapid change and great folding, 

 and discusses Suess's theory that this folding is in 

 general the result of overthrust of one land mass over 

 another. Professor Hobbs's view is that mountains 

 are raised as a result of underthrusts going out from 

 areas of subsidence, generally the ocean areas. These 

 thrusts are supposed due to shrinkage of the strata 

 under the oceans, though no attempt is made to put 

 the hypothesis on a quantitative basis. This, however, 

 is perhaps scarcely feasible as yet, and Wegener's 

 theory, which attributes the thrusts to the resistance 

 of the heavier substrata to the motion of the land 

 masses as wholes, has likewise many points of difficulty 

 about it. 



The author's theory of the origin of pockets of 

 molten lava is one of the most interesting parts of the 

 book. The rigidity of the earth is maintained under 

 conditions of internal temperature which are suffi- 

 ciently high, even relatively near the surface, for at 

 least the aqueous fusion of rock. This rigidity is due 

 to compression by the overlying load, which greatly 

 raises the fusion point. It would therefore seem as if 

 molten matter could exist only in places where the 

 weight of the upper layers has been wholly or partly 

 removed. This is supposed to occur by the folding of 



