Geology. 167 



most important and interesting. The work appears to have been 

 very well done, and the volume is valuable as a means of giving 

 chemists who are specializing in their own branches of the sci- 

 ence, some information in regard to the important achievements 

 in the other branches. It is interesting to observe that the 

 references to American researches are numerous in several of the 

 reports. This indicates that chemical investigation is being well 

 conducted in our country. h. l. w. 



II. Geology. 



1. The Origin of the Earth ; by Thomas C. Chamberlin. 

 Pp. xii, 272. Chicago, 1916 (University of Chicago Press). — 

 Geologists have long been looking forward to this book and to a 

 restatement of the planetesiraal theory by its creator. As the 

 book was written "not only for the specialist but for the educated 

 layman" as well, the subject is presented "in as summary a 

 manner and with as little technical detail as is consistent 

 with sound method." The educated layman will find the 

 book highly profitable and fairly easy to master if the author's 

 advice is taken that it were well if the reader were deliberate. 

 The specialist will also find much that is new and helpful to a 

 better understanding of the planetesimal theory. This l^poth- 

 esis, the author tells us, had its origin many years ago in an 

 endeavor to explain the climatic conditions ot" the Pleistocene 

 deposits of Wisconsin. "Strangely enough, the cold trail of the 

 ice invasion had led by this long and devious path into the 

 nebulous field of genesis " (9). 



The book begins with a discussion of the Gaseous and Laplacian 

 theories of earth origin. A ring of gas " such as the Laplacian 

 hypothesis postulates as the parent of the earth, Avith a tempera- 

 ture high enough to keep the refractory substances that make up 

 most of the earth in the form of a gas, could not have held itself 

 together by its own gravitj'." Further, it "could not have held 

 in gaseous relations the waters of the oceans or the constituents 

 of the air, nor perhaps even the rock substances of the earth" (36). 



The planetary system of the sun "must clearly have had a bi- 

 parental origin " as it clearly betrays a birth through the close 

 approach of two bodies whose tidal interactions resulted in the sun 

 taking on the form of a spiral nebula. The juvenile earth began to 

 form through the infall of theplanetesimals upon the earth-knot of 

 the nebula. The shaping agencies were primarily (1) gravitation, 

 (2) the adjustments due to the periodic shrinking of the earth 

 mass, (3) the adjustments following the periodic acceleration in 

 rotation, and (4) the pull of the moon upon the earth manifested 

 in the twice-daily tides. 



The newest feature of the book relates to the process of earth 

 shaping during the juvenile stages, a process that may be called 

 the conic hypothesis of earth structure. This theory states that 



