Gurley Telescopic Solar Compass

The Burt's Solar Compass is one of the most important surveying instruments in American history. Because of its great scarcity it is most often the featured instrument in any collection of historical surveying instruments.

The solar compass was invented by William A. Burt in 1835 and patented the next year. He designed it for surveying government public lands as a replacement for the ever-troublesome magnetic needle compass. Burt's solar compass uses a mechanical apparatus that accurately determines the true north-south direction from the sun's position in the sky.

This instrument takes Burt's invention one step further. Beginning with the 1890 USGLO manual of surveying instructions, the government directed that the important (principal) public land lines must be surveyed with the transit. According to a July-1900 Gurley catalog, the government applied this ruling so that a solar compass with telescope attachment fulfilled that requirement. Gurley had already been producing a telescope attachment for its sight vane instruments based upon its 1878 patent. Their combination of solar compass with the telescope attachment met the government standard.

Other private surveyors and government agencies also used the combination. The Smithsonian Museum has a Gurley telescopic solar compass acquired from the U.S. Geological Survey that appears the same as this example.Click here to view the Smithsonian's Gurley Telescopic Solar Compass The National Museum also provides additional historical information on the invention of the solar compass. Click here for information on the invention of the instrument. Another example of a Gurley Telescopic Solar compass can be viewed from different angles using Quick Time software. Click here to view a revolving telescopic solar compass.

Following its invention, the first of the Burt Solar Compasses were produced by Wm. J. Young in Philadelphia. Other makers soon followed, but before long the firm of W. & L.E. Gurley out-produced them all. In fact, the Gurley solar compass became the preferred instrument for surveying the millions of acres of U.S. public lands until it was eventually replaced by the solar transit. That instrument is a conventional surveyors transit to which has been added a solar mechanism that incorporates the same basic principle as developed for the solar compass.

The Gurley firm continually improved the solar mechanism for ease of adjustment and operation. This example has no serial number and was likely made either just before or just after the beginning of the 20th century. It incorporates the latest refinements and is believed to be the highest evolved form of the Burt Solar Compass.

The instrument comes with original case and a great adjustable-leg tripod complete with original protective cap. The finish on the compass is the striking brass and black that is common with Gurley surveying instruments during this period. There are some minor surface blemishes to the finish and also small areas where there is some loss of black finish. The loss of black finish is mostly along the edges of the sights and the on sighting arms where they are rubbed by the wood locking tabs when being secured inside the case. The compass includes several small tools such as the important adjuster bar, two adjusting pins, plumb bob string adjuster and screwdriver. The case is missing one of the two brass hooks for securing the lid and is scuffed on the outside but very nice inside. On the case lid is a metal tag of the Lallie Surveying Instrument and Supply Co. in Denver that acted as an agent for Gurley.

The finish on the telescope attachment is a bright lacquered brass with almost all of the lacquer intact. It accents nicely with the brass knobs and screws on the solar compass. The attachment is not original with this instrument and will also work with other Gurley compass instruments. The telescope was customarily fitted with a bracket located inside the compass case when ordered from the factory in combination with the compass. This telescope has its own separate wood case. The telescope spirit level glass has etched graduations and appears to be a replacement.

There is an excellent biography written about the inventor, William Burt, and his solar compass instrument that is titled They Left Their Mark. The author, John Burt, is a direct descendent of the inventor. A mint unopened copy of the book will be included with the compass.

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