ii8 THE POPULAR SCIENCE MONTHLY. 



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 after- 

 ward called upon to perform in the civil war. 



The efficiency of the survey was greatly increased by improved 

 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 in- 

 troduced, and secured a degree of accuracy before unknown. 

 The method of determining longitude by the exchange of star 

 signals was 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 telescope, combined with 

 the determination of longitudes from the adopted meridian by 

 the exchange of star-signals, the geographical 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 At- 

 lantic, Gulf, and Pacific coasts. The character of the Gulf Stream 

 and other currents along our coast were determined. Twice was 

 Agassiz sent to study the formation of the coral reefs of Florida, 

 and the causes that promote and restrict their growth. The mag- 

 netic constants were determined for every important point pos- 

 sible within reach of the survey. 



Other duties were assigned to Prof. Bache by the Government 

 from time to time. He was made Superintendent of Weights and 

 Measures, and in the exercise of this function directed a series 

 of investigations relative to the collection of excise duties on 

 distilled spirits, and superintended the construction of a large 

 number of sets of standard weights and measures for distribu- 

 tion to the several States of the Union. He was appointed on 

 a commission created to examine the lighthouse system of the 

 United States, and was a member of the Lighthouse Board, into 

 which this commission was merged, from its organization till 



% 



* Address in commemoration of Alexander Dallas Bache, by Benjamin Apthorp Gould, 

 delivered before the American Association for the Advancement of Science, August 6, 1868. 



