SJ&8 Blachwelder — The Geologic Hole of Phosphorus. 



large bodies of fluid magma, issuing from the interior of the 

 earth, at initial temperatures well above a thousand degrees 

 centigrade. It now seems proven beyond dispute that such 

 igneous bodies flux their way through the overlying rocks, 

 absorbing them or dissolving them as they rise. Phosphatic 

 minerals thus dissolved would later recrystallize out along with 

 the other constituents of the magma when it became a solid 

 igneous rock. It would then also appear as the mineral 

 apatite, which is apparently one of the few phosphates adapted 

 to these conditions of high temperature. As the constituents 

 of the magma obey the laws of solutions and are diffused 

 uniformly through the liquid, the apatite, like the feldspars, 

 quartz, and mica, would be eventy distributed throughout the 

 resulting igneous rock in the form of minute crystals. In so far 

 as this occurrence takes place, it closes the cycle, for it will be 

 remembered that almost at the outset of this review, phos- 

 phorus appeared in the form of microscopic apatite prisms as a 

 constituent of the typical igneous rock. Meanwhile, however, 

 the phosphorus may have passed through the complex series 

 of migrations and transformations over and over again, on and 

 near the surface of the earth. Even if the cycle should thus 

 become closed, it would be closed only temporarily, for a new 

 cycle would be initiated just as soon as the apatite of the 

 second generation became subject to the process of weathering. 



Madison, Wisconsin, 

 July 11, 1916. 



