THE TRANSCONTINENTAL ARC. 
BY 
Erasmus Darwin Preston. 
[Read before the Society February 20, 1897.] 
Introductory. 
The United States Coast and Geodetic Survey is one of the 
scientific institutions of the Government that has kept pace 
with the expansion and development of our country. Con¬ 
ceived by Thomas Jefferson one hundred years ago, estab¬ 
lished by Congress in 1807, and reorganized by President 
Tyler in 1843, it has continually adapted itself to the grow¬ 
ing needs of commerce and defense. Without departing 
from the lines of policy originally laid down, its scope has 
broadened from time to time, in response to changing con¬ 
ditions, and its details have been worked out to satisfy the 
demands of the day. 
Taking as its fundamental idea the delineation of land 
and sea in the vicinity of tide-water, the department has not 
failed to follow coordinate-lines of research when such work 
was incident to and necessary for the successful prosecution 
of its legitimate task. The spirit of the Survey has been one 
of progress. Guided by the inventive minds of Hassler, 
Bache, and Hilgard, the service early adopted radical modes 
of treatment. The application of the zenith telescope to lati¬ 
tude, the electric telegraph to longitude, the polyconic pro¬ 
jection to charts, and the plane-table to topography revealed 
new possibilities in the realm of geodesy. To these four 
agencies may be ascribed the rapidity, accuracy, and econ¬ 
omy which have characterized the production of results. 
* Published by permission of the Superintendent of the United States 
Coast and Geodetic Survey. 
29—Bull. Phil. Soc., Wash., Vol. 13. 
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