FEBRUARY 16, 1912] 
Pennsylvania in 1832. He was educated in 
the Central High School of Philadelphia, an 
institution which by the school organization 
of that time was entitled to confer college 
degrees and which had an able corps of in- 
structors. Among the faculty was Professor 
A. Dalles Bache. Professor Bache’s high re- 
gard for the young student led to his appoint- 
ment, in 1843, as magnetic observer at Girard 
College. Meanwhile Professor Bache was 
made superintendent of the United States 
Coast Survey and in 1845 young Davidson, 
then only 20 years of age, was appointed as 
clerk and computer to serve in the office of 
the superintendent. This appointment deter- 
mined his life work, for he remained in the 
service just one half century. In 1850 at his 
request he was assigned to duty on the Pacific 
coast, where for the next ten years he surveyed 
harbors, selected sites for lighthouses and de- 
termined geographical positions along the 
coast from San Diego to Puget Sound. This 
pioneer work was of the greatest importance 
to navigators, his observations during this 
period being the foundation for his “ Coast 
Pilot or Directory of the Pacific Coast,” the 
first edition of which appeared in 1857. 
At the outbreak of the civil war he was 
assigned to the Atlantic coast, where he was 
first employed as engineer on the defenses of 
the Delaware River. In 1862 he was in 
charge of the Coast Survey steamer Vizen, 
detailed for special naval service along the 
Florida coast. The next year, when Lee in- 
vaded Pennsylvania, he was made assistant 
engineer of Philadelphia. 
The frequent connection of Professor 
Davidson with important events in the history 
of the United States is well illustrated by 
his assignments for the year 1867. In Jan- 
uary he was detailed on duty as engineer of 
a party sent to the Isthmus of Panama to 
search for the best location for a ship canal. 
A few months later he was in Alaska making 
a preliminary geographical survey of that ter- 
ritory, the purchase of which was then being 
negotiated by the United States. His report 
on Alaska met the warm approval of Secretary 
of State Seward, and greatly influenced the 
SCIENCE 
259 
consummation of the purchase. One rare ac- 
complishment of Professor Davidson was his 
ability to do reconnaisance quickly and ef- 
fectively—an especially valuable quality for a 
man doing scientific work in a new country. 
In 1868 he was promoted to charge of the 
United States Coast Survey on the Pacific 
coast, a position which he retained until June, 
1895. This period was in many ways the 
richest and most productive of his life. He 
not only directed the work of the various field 
parties and personally made some notable geo- 
detie and astronomical surveys, but he also 
served on government commissions in various 
parts of the world. 
In 1872 and again in 1884 he was appointed 
by the President upon the Assay Commission 
to test the weight and fineness of the coins of 
the Philadelphia Mint, and in both instances 
made all the weighings and introduced new 
methods. Twice he was appointed by the 
Secretary of the Treasury to examine the 
assay, coin and bullion weights and the bal- 
lances and beams of the United States Mint 
at San Francisco. 
In 1873 he was appointed by President 
Grant one of the three commissioners of irri- 
gation of California, and in the following 
year was sent to China, India, Egypt and 
Europe to examine and report upon irrigation 
and reclamation works. In 1888 President 
Cleveland appointed him a member of the 
Mississippi River Commission. In 1889 he 
was appointed by President Harrison a dele- 
gate to the International Geodetic Convention 
at Paris, and was commissioned to bring to 
Washington the international prototypes of 
the standard meter and kilogram. While 
abroad on this mission he visited the observa- 
tories of Paris, Berlin and Greenwich, and 
was received with high honors. 
Many scientific societies have elected him 
to membership: Bureau des Longitudes de 
France; honorary member Berlin Geograph- 
ische Gesellschaft; Royal Geographical So- 
ciety; Scottish Royal Geographical Society; 
Swedish Society of Anthropology and Geog- 
raphy; Paris Academy, Institut de France; 
the Philadelphia Academy of Science in 18538; 
