250 Ford — Growth of Mineralogy, 1818 to 1918. 



tions and Associate Minerals/' published in the Pro- 

 ceedings of the American Philosophical Society in 1873 

 ( 13, 361 ) . Dr. Genth died in 1893. 



The period from 1860 until 1875 was not very produc- 

 tive in mineralogical investigations. The first ten vol- 

 umes of the Third Series of the Journal, covering the 

 years 1871-1876, contained mineralogical articles by only 

 some fifteen different authors. But from that time on, 

 the amount of work done and the number of investigators 

 grew rapidly. With this increase in activity came also 

 a decided change in the character of the work. The 

 period between 1871 and 1895 can be characterized as one 

 in which all the various aspects of mineral investigation 

 received more nearly equal prominence. While the 

 chemical composition of minerals still held rightly its 

 prominent place, the investigation of the crystallographic 

 and optical characters and the relationships existing 

 between all three were of much more frequent occurrence. 

 Edward S. Dana commenced his scientific work by pub- 

 lishing in 1872 an article on the crystals of datolite which 

 was probably the first American article concerned wholly 

 with the description of the crystallography of a mineral. 

 Samuel L. Penfield began his important investigations in 

 1877 and the first articles by Frank W. Clarke appeared 

 during this period. The first edition of the Text Book 

 of Mineralogy by Edward S. Dana with its important 

 chapters on Crystallography and Optical Mineralogy 

 was published in 1877 and his revision of the System of 

 Mineralogy (sixth edition) appeared in 1892. 



Unquestionably the foremost figure in American min- 

 eralogy during this period was that of Samuel L. Pen- 

 field. He embodied in an unusual degree the characters 

 making for success in this science, for few investigators 

 in mineralogy have shown, as he did, equal facility in all 

 branches of descriptive mineralogy. He was a skilled 

 chemist and possessed in a high degree that ingenuity in 

 manipulation so necessary to a great analyst. He was 

 also an accurate and resourceful crystallographer and 

 optical mineralogist. His contributions to the science of 

 mineralogy can be partially judged by the following 

 brief summary of his work. He published over eighty 

 mineralogical papers, practically all of which were 

 printed in this Journal. These included the descriptions 

 of fourteen new mineral species, the establishment of the 



