Page:Popular Science Monthly Volume 48.djvu/128

118 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 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 introduced, 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 Atlantic, 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 magnetic constants were determined for every important point possible 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 ou distilled spirits, and superintended the construction of a large number of sets of standard weights and measures for distribution 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