236 LEADING AMERICAN MEN OF SCIENCE 



aspirations of the young scientist was his appointment as assist- 

 ant to Professor Silliman in 1836. The routine duties of the posi 

 tion occupied but little time. He had the benefit of stimulating 

 association with other scientific men, and the use of the library and 

 the already respectable mineralogical collection of the college. 



His studies at this period were chiefly in mineralogy; and in 

 1837 appeared the first of his great scientific works, the System 

 of Mineralogy. It is certainly remarkable that a book represent- 

 ing so large an amount of research should have been produced by 

 a man only twenty-four years old, and only four years out of 

 college. Successive editions of the work were published in 1844, 

 1850, 1854, and 1868. In the fifth edition Professor Dana had 

 the assistance of Professor George J. Brush. That edition in- 

 cluded only descriptive mineralogy, but was more voluminous 

 than the previous editions which had included crystallography 

 also. A sixth edition, completely rewritten by Professor Edward 

 S. Dana, the son of James D. Dana, was published in 1892. 



The four years from the summer of 1838 to that of 1842 stand 

 strongly in contrast with the remainder of Professor Dana's career. 

 In those years he had an experience of the adventures, the hard- 

 ships, and perils, and no less of the joys, of the explorer of unknown 

 lands and seas. The remainder of his life was in the main the 

 quiet and uneventful life of the student. To him, as to his great 

 contemporary, Charles Darwin, a period of world-wide travel, 

 coming early in his career, with its opportunities of seeing most 

 varied aspects of nature and life, was doubtless of immense value 

 in storing his memory with material for scientific thought, and in 

 leading him to broad vjfiw-j^gfjx)smic jprf^ggggiv Most of all to a 

 geologist is wide and varied travel an experience of inestimable 

 importance. 



The United States Exploring Expedition, under the command 

 of Lieutenant (afterwards Admiral) Charles Wilkes, sailed from 

 Norfolk, Virginia, August 18, 1838. The expedition consisted of 

 six vessels the Vincennes, the Peacock, the Porpoise, the Relief, 

 the Sea-gull, and the Flying-fish. Of these, the first two were 

 sloops-of-war, and were the principal vessels of the little squadron. 



