REVIEWS 395 



receives an increase of temperature, this increment will be expended 

 in melting more of the surrounding rock rather than in raising the 

 temperature of the already molten mass. 



Concluding, therefore, that his theoretical inspection proves that 

 differentiation can at most play only a minor part in the explanation 

 of consanguineous rocks, he advances his theory of the original 

 heterogeneity of the earth. 



The points advanced for such a heterogeneity are as follows : 



1. The land and water hemispheres. 



2. Anomalies in gravity. 



3. Distribution of feldspars in the west. 



4. Distribution of metallic ores. 



5. The seeming permanence of continental plateaus show this 

 heterogeneity to be original. 



6. Condensation from nebulous ring would forbid perfect homo- 

 geneity. 



7. The viscosity of the fluid earth would permit only a rude approx- 

 imation to uniformity of composition. 



8. Hypogeal refusion results in a re-formation of a heterogeneous 

 liquid. 



9. The transitional series of erupted lavas may be explained by 

 chance mixing of unlike magmas. 



No attempts will be made to criticise Dr. Becker's views on the het- 

 erogeneous composition of the earth. Many of his points are strong, 

 and have been advanced by others against the conception of a primitive 

 homogeneous earth. Yet his application of physico-chemical princi- 

 ples is open to investigation. 



Dr. Becker is doubtless correct in his conclusion that any change in 

 relative concentration of miscible liquids by means of differential pres- 

 sure or temperature is inadequate to explain any considerable diffusion 

 of a magma. Prior to Dr. Becker, Dr. Backstrom pointed this out 

 very clearly. Nevertheless we may be permitted to examine some of 

 the facts he cites and inferences he draws to prove this point. 



He says there are onl}^ two conceivable ways in which differentia- 

 tion may occur; either by segregation into miscible or into immiscible 

 liquids, caused by differential pressure, or temperature or both. May 

 not these two operations be assisted by the cr3'stallizing of different 

 double salts at different temperatures and pressures peculiar to each ? 



