lt!S Scientific Intelligence. 



the eartb is divided into six primary, positive, rigid, conic 

 segments of crystalline substance but non-crystalline major 

 Structure, whose apices unite at the center of the earth, and 

 between which lie the more or less irregular, laterally crowded, 

 weaker, negative and lighter continental wedges. Two of the 

 master cones occupy the Pacific depression, two the Atlantic, one 

 the Indian, and the sixth takes in the more or less positive 

 Mediterranean-Black Sea-Caspian Sea region. The segments 

 move upon one another along "yield tracts" or fissure tracts that 

 radiate from each pole at angles of about 120°. This hypothesis 

 appears to be diametrically opposed to the working hypothesis 

 of i^ostasy and the hitter's postulate that the relief of the earth's 

 surface is compensated for by corresponding variations in sub- 

 surface density which cease at a depth equal to a fiftieth or a 

 hundredth part of the radius of the earth. The book, however, 

 does not follow the digressions in discussions which arc necessary 

 in pursuing the method of multiple working hypotheses. The 

 popular nature of the book was doubtless regarded as a bar to 

 such thorough discussion and comparison of conflicting hypo- 

 theses. 



The inner reorganization of the earth is due to compression, 

 generation of heat, and, through atomic dissociation, the birth of 

 radioactive elements. " Radioactive heat was thus added to the 

 heat of compression., ... It is therefore assumed that there was 

 only a sparse distribution of radioactive elements in the parent 

 nebula, and hence in the original material of the earth, but that 

 there was progressive concentration of these at the surface as effu- 

 sive igneous action went on " (227-228). In the course of time the 

 metals and metallic alloys probably concentrated toward the 

 center of the earth and the silicates toward the surface (237). 



c. s. 



2. Jointing as a Fundamental Factor in the Degradation of 

 the Z,ithot<phere ; by Frederick Ehrenfeld. Proc. Amer. 

 Philos. Soc, vol. Iv, 1916, pp. 363-399, pis. vi-viii. — A very sug- 

 gestive pajser the conclusions of which are as follows : "Law of 

 joints. — 1. The lithosphere is subject by its nature to the develop- 

 ment of lines of weakness or fracturing which in turu develop 

 into actual movable segments. These segments or joint lines 

 develop in such regularity of arrangement that they may be said 

 to occur in ' joint- systems ' which are shown at the surface as 

 controlling agents in land erosion and land shaping ; and they act 

 beneath the surface inducing tectonic movements which are in- 

 dependent of atmospheric or marine contact. 



" 2. Degradation of the lithosphere is fundamentally a factor 

 in its own structure and will occur wherever an agent capable of 

 transporting the movable joint blocks is in contact with the 

 lithosphere. This applies to those portions of the land or rock 

 mass below sea level. 



" 3. Atmospheric erosion and marine planation are two separate 

 phases of a general process of lithosphere degradation which are 



