270 A CENTURY OF SCIENCE 



light was discovered by Mains in 1808, and in 1813 

 Brewster first recognized the optical differences between 

 uniaxial and biaxial minerals. The modern science of 

 chemistry was also just beginning to develop at this 

 period, enabling mineralogists to make analyses more 

 and more accurately and thus by chemical means to 

 establish the true character of minerals, and to properly 

 classify them. 



Franz von Kobell, on page 372 of his ' ' Geschichte der 

 Mineralogie, " somewhat poetically describes the condi- 

 dition of the science at this period as follows : "With the 

 end of the eighteenth and the commencement of the nine- 

 teenth centuries exact investigations in mineralogy first 

 began. The mineralogist was no longer content with 

 approximate descriptions of minerals, but strove rather 

 to separate the essential facts from those that were acci- 

 dental, to discover definite laws, and to learn the rela- 

 tions between the physical and chemical characters of a 

 mineral. The use of mathematics gave a new aspect to 

 crystallography, and the development of the optical 

 relationships opened a magnificent field of wonderful 

 phenomena which can be described as a garden gay with 

 flowers of light, charming in themselves and interesting 

 in their relations to the forces which guide and govern the 

 regular structure of matter. ' ' 



In the Medical Repository (vol. 2, p. 114, New York, 

 1799), there occurs the following notice : "Since the pub- 

 lication of the last number of the Repository an Associa- 

 tion has been formed in the city of New York 'for the 

 investigation of the Mineral and Fossil bodies which com- 

 pose the fabric of the Globe; and, more especially, for 

 the Natural and Chemical History of the Minerals and 

 Fossils of the United States,' by the name and style 

 of The American Mineralogical Society." With this 

 announcement is given an advertisement in which the 

 society "earnestly solicits the citizens of the United 

 States to communicate to them, on all mineralogical sub- 

 jects, but especially on the following: 1, concerning 

 stones suitable for gun flints ; 2, concerning native brim- 

 stone or sulphur ; 3, concerning salt-petre ; 4, concerning 

 mines and ores of lead." Further the society asks "that 



