922 



SCIENCE 



[N. S. Vol. XXXII. No. 834 



Causal Geology. By E. H. L. Schwarz, Pro- 

 fessor of Geology at the Ehodes University 

 College, Grahamstown, South Africa. 

 Glasgow, Blackie & Son ; New York, D. Van 

 Nostrand Company. Pp. 248, with numer- 

 ous figures and plates. $2.50. 

 The aim of this treatise is set forth by the 



author in his preface in the following words : 



In the ten years spent on the Geological Survey 

 of the Colony of the Cape of Good Hope I was 

 brought into contact with most of the geological 

 problems that are presented by our earth in a 

 way which, I believe, is aflforded nowhere else. 

 The whole country, practically, is bare of soil and 

 the rocks lie ready to the hammer everywhere, 

 while the enormous gashes sawn through the land 

 by the rivers reveal sections of unparalleled mag- 

 nitude and clearness. As year by year went by 

 the facts presented themselves to me in an order 

 different from that stated in the text-books, and 

 the theories as to their origin and nature became 

 simplified and different from established ones. 

 There seemed to me no need to speculate on enig- 

 matical problems, but the facts observed, if al- 

 lowed to arrange themselves according to their 

 natural sequence, explained many of the problems 

 that are the subject of so much controversy. I 

 feared that in the isolation from centers of cur- 

 rent geological thought I had gone off on a side 

 track which led nowhere, but the publication of 

 Professor T. C. Chamberlin's " Planetismal Hy- 

 pothesis " ' showed me that I was traveling in a 

 direction which, at least, was being taken by 

 others. The planetismal hypothesis allows known 

 facts to weigh more than theories, and enables one 

 to build up a system of geology without an appeal 

 to the unknown and unknowable. It is not for me 

 to judge the merits of this hypothesis, but in my 

 opinion it is the most positive advance in natural 

 science that has been made for a very long time. 

 ... In many cases I have gone much further than 

 Professor Chamberlin, but the object I have set 

 before me is to lay the whole ease from the single 

 point of view of a solid earth. 



The author in the first chapter makes five 

 postulates concerning which he remarks that, 

 while he can not prove them, " they are gen- 



'T. C. Chamberlin, "Year Book Carnegie In- 

 stitution," No. 3, 1905, pp. 208-253 ; T. C. Cham- 

 berlin and R. D. Salisbury, " Geology," " Earth 

 History," Vol. II., London, 1906, pp. 38-81. 



eral conceptions which follow naturally from 

 the investigation of geological phenomena and 

 that where current ideas differ from them 

 there has interposed between the fact and the 

 conclusion theories brought in from other sci- 

 ences or developed within the domain of geol- 

 ogy, and these have served as a screen which 

 has blurred the outline of objects." 



These are: (1) That the rocks of the earth's 

 crust are in constant motion. (2) That the 

 force of cohesion in rocks is insufficient to 

 keep them rigid when in large masses, the ro- 

 tational force of the earth being thus quite 

 competent to mould the cold and solid earth 

 into the shape which it possesses — that which 

 would be adopted by a revolving fluid mass. 

 (3) That the area of the surface of the globe is 

 not a diminishing one. (4) The surface of 

 the earth is uniform in average texture 

 throughout. The continental masses are thus 

 not relatively lighter than the suboceanic por- 

 tions of the earth's surface and the theory of 

 the permanence of ocean basins must be aban- 

 doned. (5) That the earth is growing by the 

 addition of meteoric matter and the composi- 

 tion of the earth, as a whole, is represented by 

 the average composition of this matter. While 

 this is true, the exterior portion of the earth's 

 crust has been worked over and over by proc- 

 esses of weathering and erosion during which 

 the more soluble substances, principally iron 

 and magnesium, have been carried away in 

 solution downward, toward the earth's center, 

 leaving behind a residue more siliceous than 

 the average composition of the globe. 



Taking these postulates which he considers 

 to be true, as granted, the author then explains 

 the geological processes at work within the 

 earth and upon its surface. The accession to 

 the material of the earth's surface by the fall 

 of meteorites is considered at length and in 

 the case of Coon Butte it is stated that there 

 seems to be no reasonable doubt that this 

 crater is actually the result of the impact of a 

 huge bolide. Turning then to the moon as 

 illustrating a stage in the earth's evolution, 

 the author considers that the hypothesis which 

 best explains the maria, is that great meteors 

 fell upon the moon, and by their impact pro- 



