8 The Oregon Surveyor | Vol. 45, No. 4 Featured Article running the lines thereon noted.” Tiffin’s Instruction of 1815 (the first written instructions issued by the GLO to its Deputy Surveyors) specified “a good compass of Rittenhouse construction, have a nonius division...” This is a vernier compass, “nonius division” meaning a vernier. Thus, the vernier compass became the standard instrument for surveys of the USPLSS. Until... William Austin Burt and his Solar Compass William Austin Burt (1792–1858) was a GLO Deputy Surveyor, who, in 1835 while laying out townships in Wisconsin, noted unusual deviations in the lines surveyed using his compass. He began work on a method and form of compass that would determine the direction of the true meridian independent of magnetic north. He invented an ingenious device that uses the observer’s latitude, the sun’s declination, and local time to determine true north. The device mechanically solves the PZS (Pole-Zenith-Star) Triangle. The prominent Philadelphia maker, William J. Young (1800–1870) built the device, and Burt was awarded Patent 9428X on February 25, 1836. Burt made improvements to his solar compass and an improved version was patented in 1840. In 1850, Burt’s patent expired, which allowed other makers to produce the solar compass. (The circumstances of the expired patent are a sad story.) There are about 12 known post1850 makers of solar compasses. All the solar compasses made prior to 1850 are marked “Burt’s Patent” and “W.J. Young” or “Wm. J. Young,” he having made them. They are not dated or numbered. Those made by Young after about 1852 are numbered. Is it a transit or a theodolite? Generally, the theodolite refers to an instrument with divided circles to measure both horizontal and vertical angles to high precision, the telescope is relatively long and will not transit (rotate 360 degrees) about its horizontal axis. The more common term “transit” refers to an instrument with both horizontal and vertical circles (only horizontal on early transits), a 4-screw leveling head, bubbles for leveling and a telescope that will transit. William J. Young is credited with building the first dividing engine in America. That allowed him to cut circles and he is credited with building the first American transit in 1831. The transit developed and attachments, such as a variation on Burt’s solar compass, was added by many manufacturers. For mining applications, parallel telescopes were added, thus allowing sightings at large vertical angles into steep mine shafts. Large precise transits were constructed for control surveys and astronomical observations. Horizontal circle diameters can be as large as 18 inches. Solar transit by W. & L.E. Gurley; Troy, New York. continued Gimbaled compass by James Reed (1792–1878) of Pittsburgh. Used in the mines.
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