ALEXANDER DALLAS BACHE. 443 



survey had not reached and had great influence in winning 

 public favour for the survey. He had a wonderful faculty for 

 enlisting the efforts and talents of others in carrying out his 

 plans. " As rapidly as means allowed, the services of American 

 scientists throughout the land were enlisted in aid of the survey, 

 and the whole intellectual resources of the country thus made 

 tributary to its usefulness and success. Thus Walker, Peirce, 

 Bailey, Agassiz, Barnard, Kendall, Mitchell, Bond, Alexander, 

 and many others, were called on to assist in the advancement 

 of the undertaking ; and this large and wise policy prevailed 

 during the whole period of his superintendence." * Many of 

 the ablest officers of the navy and the army were brought into 

 the Coast Survey service, and gained experience of great value 

 in the duties many of them were afterward called upon to per- 

 form in the civil war. 



The efficiency of the survey was greatly increased by im- 

 proved instrumental equipment. Antiquated instruments were 

 replaced by those of the most improved type ; an apparatus for 

 the measurement of base lines, invented by Prof. Bache, was 

 introduced, and secured a degree of accuracy before unknown. 

 The method of determining longitude by the exchange of star 

 signals were developed through the agency of Sears C. Walker. 

 Prof. Gould has stated that he had received accounts of this 

 important advance in geodetic practice from the lips of both 

 Bache and Walker, and that " their descriptions varied but in 

 one salient point, namely, that each ascribed the chief merit to 

 the other." The determination of latitudes with the zenith 

 telescope, by Talcott's method, first tested in 1845, was early 

 adopted by the survey. " Thus by the use of the zenith tele- 

 scope, combined with the determination of longitudes from the 

 adopted meridian by the exchange of star signals, the geo- 

 graphical position of the primary astronomical stations of the 

 survey could claim, ten or fifteen years ago, to be determined 

 with more accuracy than that of any European observatory." 



Stations for tidal observation were established all along the 

 Atlantic, Gulf, and Pacific coasts. The character of the Gulf 

 Stream and other currents along our coast were determined. 



* Address in commemoration of Alexander Dallas Bache, by Benjamin 

 Apthorp Gould, delivered before the American Association for the Advance- 

 ment of Science, Aug. 6, 1868. 



