58 EDWARD S. HOLDEN 



of Rowland. The use of a telescope as a collimator was first 

 proposed by Rittenhouse. The pioneer opticians of the 

 United States were Holcomb (1826), Fitz (1846 or earlier), 

 Clark (1845), Spencer (1851). Only the Clarks have a world 

 ivride reputation. Wiirdemann, instrument maker to the 

 "United States Coast Survey (1834), had a decided influence 

 on observers and instrument makers throughout the United 

 States, as he introduced extreme German methods and 

 models among us, where extreme English methods had pre- 

 viously prevailed. The system of rectangular land surveys, 

 which proved to be so convenient for the public lands east of 

 the Rocky mountains, was devised and executed by Mans- 

 field, a graduate of the military academy. 



The list of army officers who became distinguished in 

 civil life as professors in the colleges of the country is a very 

 long one. Courtenay (class of 1821 at West Point) was pro- 

 fessor of mathematics at the university of Pennsylvania, 

 1834-1836; at the university of Virginia, 1842-43, and was 

 the author of admirable text books. Norton (class of 1831) 

 became professor at New Haven, and wrote a very useful 

 text book of astronomy in 1839 ; and the list could be much 

 extended. The excellent training in mathematics at West 

 Point (chiefly in French methods) early made itself felt 

 throughout the whole country. The mathematical text 

 books of Peirce, of Harvard, and of Chauvenet, of the Naval 

 academy, brought the latest learning of Europe to American 

 students. Mitchell (class of 1829 at West Point) was the only 

 graduate who became a professional astronomer (1842-1861). 

 His direct service to practical observing astronomy is small, 

 but his lectures (1842-1848), the conduct of the Cincinnati 

 observatory (1845-1859), and his publication of the Sidereal 

 Messenger (1846-1848), together with his popular books, 

 excited an intense and widespread public interest in the 

 science, and indirectly led to the foundation of many observa- 

 tories. He was early concerned in the matter of using the 

 electric current for longitude determinations, and his appara- 

 tus was only displaced because of the superior excellence of 

 the chronograph devised by the Bonds His work was done 

 under immense disadvantages, in a new community (Ohio), 



