GROWTH OF MINERALOGY 269 



century, that any further notable progress was made. 

 Agricola (1494-1555) was a physician, who, for a time, 

 lived in the mining district of Joachimstal. He studied 

 and described the minerals that he collected there. He 

 was the first to give careful and critical descriptions of 

 minerals, of their crystals and general physical proper- 

 ties. Unfortunately, he also did not realize the funda- 

 mental distinction between fossils and minerals, and 

 probably because of his influence this error persisted, 

 even until the middle of the eighteenth century. But, 

 naturally, as the number of scientific students increased, 

 the number of those who rejected this conclusion grew, 

 until at last, the true character of fossils was established. 

 The keen interest in minerals and fossils which was 

 aroused by this controversy, together with the rapid 

 extension of mining operations, drew the attention of 

 scientific men to other features of the earth's surface 

 and led to a more extended investigation of its characters 

 and thus to the development of geology proper. It is 

 interesting to note also that mineralogy was the first of 

 the Geological Sciences to be officially recognized and 

 taught by the universities. 



Although, as has been shown, the beginnings of min- 

 eralogy lie in the remote past, the science, as we know it 

 to-day, can be said to have had practically its whole 

 growth during the last one hundred years. Of the more 

 than one thousand mineral species that may now be con- 

 sidered as definitely established hardly more than two 

 hundred were known in the year 1800 and these were only 

 partially described or understood. It is true that Haiiy, 

 the "father of crystallography, " had before this date dis- 

 covered and formulated the laws of crystal symmetry, 

 and had shown that rational relations existed between 

 the intercepts upon the axes of the different faces of a 

 crystal. It was not until 1809, however, that Wollaston 

 described the first form of a reflecting goniometer, and 

 thus made possible the beginning of exact investigation 

 of crystals. The distinctions between the different crys- 

 tal groups were developed by Bernhardi, Weiss and Mohs 

 between the years 1807 and 1820, while the Naumann 

 system of crystal symbols was not proposed until 1826. 

 The fact that doubly refracting minerals also polarize 



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