THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Aet. XXYI. — The Lime-Silica Series of Minerals: * by 

 Arthur L. Day and E. S. Shepherd, with Optical Study 

 by Fred E. Wright^ 



Part I. Introductory. 



Axyoxe who has followed the work of the eminent Norwe- 

 gian scientist, Prof. J. H. L. Vogt, during the past three or 

 four years, must realize that an extraordinarily effective 

 weapon has come into the service of petrology, the full power 

 of which cannot at once be understood or appreciated. We 

 refer to the methods and established generalizations of physi- 

 cal chemistry. The older science of chemistry has made such 

 strides under these new theories of solutions that we really 

 have little more to do than to apply them ready-made to our 

 own problems, like a smooth and powerful machine tool of 

 guaranteed effectiveness. Mineral solutions, as Bunsenlong ago 

 maintained, are after all only chemical solutions over again with 

 slightly different components and a different, a very different, 

 range of temperatures and pressures. There is no need to 

 disparage the difficulties involved in operating at high tem- 

 peratures and under great pressures; they are very great, 

 probably even greater than most of us appreciate, but they are 

 certainly not insuperable, and when they are overcome, not 

 only will a new era in the science of petrology have been 

 inaugurated but an important return service will have been 

 rendered to physics and physical chemistry in extending the 

 scope of their generalizations. 



There is, therefore, no question of where to begin. Kooze- 

 boom, Vogt, and many others have seen and appreciated and 

 indicated to us with great clearness the various ways in which 



* Full text of a paper of this title read before the American Chemical 

 Society at the Ithaca meeting. June 28, 1906. 



f The authors are indebted to Prof. A. C. Gill of Cornell University for 

 a number of microscopic examinations of our earlier products, and for 

 many helpful suggestions. 



am. Jour. Sci. — Fourth Series, Yol. XXII, No. 130.— October, 1906. 

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