August 18, 1916] 



SCIENCE 



243 



argued that a cracking would occur, giving 

 three yield zones which tended to be at angles 

 of 120 degrees to each other. These radiated 

 from the poles after the analogy of the hexa- 

 gonal columnar jointing of basaltic columns 

 due to shrinkage in cooling. These yield zones 

 in vertical meridional planes, it is argued, 

 would, again after the analogy of the basaltic 

 columns, be the elevated zones and determine 

 the larger outlines of the initial continents. 

 There would result six great oceanic basins, 

 counting the Mediterranean as one. These 

 oceanic basins are conceived to be the some- 

 what circular bases of cones of slightly heavier 

 material built up during earth-growth and 

 having their apices deep in the centrosphere. 

 By periodic settling of these heavier master 

 segments the continental yield tracts between 

 are squeezed up and made more protuberant. 



This hypothesis of juvenile shaping is of 

 course, like the other steps in the development 

 of the planetesimal hypothesis, dependent upon 

 the basal postulates. It is not clear that earth- 

 strains due to the causes invoked could initiate 

 such a primary segmentation, in fact calcula- 

 tions on the stresses which the reviewer has 

 made to test this sub-hypothesis pointed to 

 quite a different method of yielding. The dis- 

 tribution of continents and oceans does not 

 accord very closely with it, and the evidence 

 of isostasy does not indicate that the density 

 differences between continents and ocean basins 

 reach below the outer fiftieth of the earth's 

 radius. This hypothesis of juvenile shaping 

 should therefore be accepted with much re- 

 serve and does not appear to be as well sup- 

 ported as are the conclusions of the previous 

 chapters. 



Chapter IX. is on The Inner Reorganization 

 of the Juvenile Earth. The particles of radio- 

 active matter would tend toward local heating 

 and fusion. Thus they would be progressively 

 concentrated into the outer shell of the earth 

 by the rising of igneous matter. Pulsatory 

 stresses from body tides and from shrinkage 

 are regarded as the chief agents leading fused 

 matter outward and serving to maintain the 

 earth's body in solid form. 



Chapter X is on Higher Organization in 



the Great Contact Horizons. This is a dis- 

 cussion of the conditions which it is thought 

 favored the rise of life on the surface of the 

 globe. The most favorable environment for 

 this great step in protoplasmic synthesis is 

 regarded as being in the soil layer of the land, 

 the contact horizon of earth, water, air and 

 sunlight. The conditions of planetesimal in- 

 fall and of the lack of devouring cells would 

 have especially favored the process during the 

 later growth stages of the earth. 



Having given this summary of the volume, 

 some statements may be made in regard to it 

 as a whole. It must impress every reader as a 

 notable constructive addition to thought upon 

 this fundamental subject. Chamberlin follows 

 his postulates to their logical conclusion, even 

 though this must involve the building of hy- 

 pothesis upon hypothesis. He wisely con- 

 siders this preferable to no attempt in the 

 direction of complete solution. But the limits 

 of the book and the nature of the Science 

 Series to which it conforms preclude him from 

 following that method of multiple working hy- 

 potheses which he had elsewhere used and the 

 necessity for which he has urged in an article 

 which every scientist should read. 1 This 

 method is especially desirable where there are 

 alternative postulates which have not been 

 disproved. Ko one realizes more strongly than 

 Chamberlin, however, the preliminary and 

 tentative nature of many of his conclusions, 

 owing to the nature of his postulates. 2 



Because of the submergence of the method 

 of multiple working hypotheses, however, the 

 lay reader and even those geologists who do 

 not go into the literature behind the volume 

 will be apt to obtain too narrow and rigid a 

 conception of the limits of the planetesimal 

 hypothesis. Each section seems so convincing 

 upon a first reading that it may appear as if 

 future work must be built as added stories or 

 as finishings to the present structure; whereas 

 the lower stories appear in fact so broad and 



i ' ' Studies for Students. The Method of Mul- 

 tiple "Working Hypothesis." Jour. Geol., V., 837- 

 848 (1897). 



2 See especially pp. 171 and 223 for his com- 

 ments. 



