PROF. JAMES D. DANA. 363 



often interfere with the awards of justice ; but here, more than any- 

 where else, errors of personality are eliminated by the impersonal tri- 

 bunal to which all questions are at last referred. A pretty definite idea 

 is conveyed, when it is said that a man has " mastered a science." He 

 must have made himself familiar with a certain body of facts and prin- 

 ciples, with their historic growth and their degree of development. 

 But the familiarity here implied is not that which is current in the 

 walks of literature. It is not to be gained merely by reading. It im- 

 plies a direct knowledge of the phenomena themselves knowledge at 

 first hand and the exactions in this sphere of thought go further still. 

 A man cannot be said to have mastered a science until he has thor- 

 oughly possessed himself of its method of research, and proved this 

 thoroughness by successful, original work. He must have contributed 

 to its advancement, to its original stock of observations and inductions, 

 and done it so effectually that those who stand highest shall recognize 

 the validity and value of his work. This condition being complied 

 with, the number of sciences that have been successfully pursued, and 

 the degree of their complexity, become fair measures of the mental 

 breadth, grasp, and power of the minds engaged upon them. Hum- 

 boldt was preeminent because of his conquest of many sciences. Helm- 

 holtz has a high place in European science because he is confessedly 

 strong in mathematics, physics, and physiology, and has combined the 

 researches of these sciences in carrying on his original investigations. 

 Judged by this standard, the subject of the present sketch must be as- 

 signed an eminent position in American science, as he is an acknowl- 

 edged master in the three extensive departments of mineralogy, geolo- 

 gy, and zoology, having made original investigations of great value in 

 all these fields of study. 



Prof. Dana was born, in 1813, in Utica, New York, where he passed 

 the first years of his life. He seems to have had an early inclination 

 to the sciences, as at seventeen years of age he entered Yale College, 

 attracted by the fame of Prof. Silliman (Sr.), the distinguished pio- 

 neer in American science. During the regular course of study at New 

 Haven, Mr. Dana evinced an especial love for the natural sciences, 

 without neglecting philological and mathematical pursuits, in the lat- 

 ter of which he was distinguished. He was graduated with honor, 

 Bachelor of Arts, in 1833, and about the same time received the ap- 

 pointment of teacher of mathematics to midshipmen in the Navy of the 

 United States. In that capacity, he sailed to the Mediterranean, in 

 the United States ship-of-the-line Delaware, returning in 1835. During 

 the two years following, he acted at Yale College as assistant to 

 the distinguished professor whose successor in office he afterward 

 became. 



In December, 1836, he was appointed mineralogist and geologist of 

 the Exploring Expedition then about to be sent by the Government 

 of the United States to the Southern and Pacific Oceans. The five 



