The value of the study of chemical reactions under the microscope and the recognition of precipitates by their characteristic geometrical and optical properties has long been known. As early as 1867 Wormley (28) published a treatise on the microchemistry of poisons. Bořický (4) was the pioneer in the application of microchemical tests to minerals. In 1877 he stated his hope of developing a “universal method” for analysis of rock-forming minerals by means of the recognition of the characteristic fluosilicates of the metallic elements. His work gave impetus to a rapid development of microchemistry, which movement lasted until the end of the century. During that period Streng, Haushofer, McMahon, Klement and Renard, Huysse, Behrens, and others made highly valuable contributions. How closely the development of microchemistry was associated with petrography and mineralogy is readily apparent on noting the principal field of interest of the above mentioned workers.