THE 



AMERICANJOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. XXXII. — The Geologic Role of Phosphorus ;* by Eliot 

 Black welder. 



Progress in scientific research is attained largely by the 

 most intensive study of minute problems ; but it is also neces- 

 sary that there should be frequent attempts to view these 

 problems in their larger relations. Such undertakings are 

 always the more hazardous for the student because they oblige 

 him to reach out of his special field into domains with which 

 he may have only a general acquaintance. In preparing this 

 paper on the part plajed by phosphorus in geologic processes, 

 the writer has tried not only to correlate his work with that of 

 many other students in this and other countries, but also to 

 understand the bearing of sister sciences upon the subject. 

 He has done so with keen realization of the pitfalls that beset 

 the path especially outside his own limited field. f 



Phosphorus occurs naturally in many different forms and 

 situations. Nevertheless, its varied transformations follow an 

 orderly sequence, which is in harmony with the general scheme 

 of rock metamorphism and biologic evolution. In a broad 

 way, these changes form a cycle within which there are sub- 

 ordinate cycles, all having a common beginning, and probably 

 capable of being brought to a common end. Any particular 

 atom of phosphorus may follow one or more of the subordinate 

 cycles while another atom may pursue a different route. 



The primary occurrence of phosphorus in the earth, like the 

 beginnings of most things in geology, lies wholly in the realm 



* Presented in summary before the Geological Society of America at 

 Washington, December 29, 1915. 



f For valuable information and advice the writer is indebted to his col- 

 leagues, Professors E. V. McCollum and E. B. Hart, of the University of 

 Wisconsin, Mr. Chauncey Juday of the Wisconsin Geological and Natural 

 History Survey, and Prof. W. A. Noyes of the University of Illinois. 



Am. Jour. Sci. — Fourth Series, Vol. XLII, No. 250. — October, 1916. 

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