A solar compass is a railroad compass with a solar attachment that allows
surveyors to determine the north direction by reference to the sun rather than
by reference to the magnetic needle. The form originated with William Austin
Burt, a United States Deputy Surveyor who began surveying government lands in
Michigan in 1833. In 1835, while working in an area of Wisconsin where there
were large deposits of iron ore, Burt experienced great difficulty in using his
standard vernier compass. By December he had roughed out his ideas for a solar
compass, and asked William J. Young in Philadelphia to make a model that he
could submit to the Patent Office. Burt received a patent (#9428) the following
year, and the Franklin Institute awarded him the Scott’s Medal for this
"ingenious" instrument. But, as the solar compass was not yet
serviceable, Burt went back to the drawing board. In 1840, confident that he had
solved all the problems of his design, Burt asked Young to produce solar
compasses. In 1850, the year that Burt’s patent expired, the General Land
Office adopted the solar compass as a standard instrument for all major boundary
lines in regions of magnetic disturbance, and demand rose accordingly. Claiming
that he had never received even $300 "for his right in said
invention," Burt petitioned Congress to renew his patent. But to no avail.
Burt’s solar apparatus consists of three arcs: one for setting the latitude
of the land to be surveyed; one for setting the declination of the sun; and one
for setting the hour of the day. In the latter half of the 19th century, several
instrument makers offered solar attachments of this sort that could be used with
transit instruments.
Ref:
William A. Burt, Description of the Solar Compass (Detroit, 1844).
William A. Burt, A Key to the Solar Compass, and Surveyor’s Companion
(Philadelphia, 1855).
John Burt, History of the Solar Compass Invented by Wm. A. Burt
(Detroit, 1878).
