Beautifully Restored Light Mountain Solar Transit with Jones Latitude Arc

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The Gurley Light Mountain Solar Transit with a Jones Latitude Arc offered here is a INCREDIBLE example of one of the most important surveying instruments ever made for public land surveys. Having looked thru a great number of General Land Office field notes for the public land states, I estimate that US Deputy Surveyors and Mineral Surveyors used a Gurley Light Mountain solar transit in approximately 30% of the public land and mineral surveys from 1880 thru 1910. That's just sheer marketplace domination when you consider all of the different solar compasses and solar transits made by instrument makers.

William Schmolz in San Francisco patented the idea of putting a Burt solar until on a transit, and then sold the rights to the patent to Gurley in the early 1870s. Gurley then had the exclusive ability to manufactures and sell solar transits. Shortly thereafter, in 1876 Gurley created the Gurley the Light Mountain Transit as a light-weight alternative to Gurley's more robust Engineer's and Surveyor's transit. Putting the Burt solar unit on top of a light mountain transit combined light weight with GLO mandated accuracy, and was a match made in heaven. Gurley production records indicate that sales of light mountain solar transits exceeded sales of all other Gurley solar transits by a 4 to 1 margin form 1875 to 1885.

Gurley owned the solar transit market for years, until other approaches (Saegmuller solar attachments, Smith solar attachments, etc) to making solar observations were developed by other makers. (See a 1901 History of Solar Instruments here). Gurley still dominated the market for solar transits even after competitive approaches hit the market - Gurley's head start in making solar transits proved insurmountable although competitors like Young & Sons and Buff and Buff chipped away at Gurley's huge marketshare year after year. Gurley's domination of the solar transit market came to an end in 1910 or so, when the GLO terminated hiring surveyors on a contract basis and hired them instead as employees. Starting around 1910, the GLO started buying solar instruments to outfit all of its newly hired surveyors from Young & Sons, and a few years later from Buff & Buff. The GLO purchased very few solar transits form Gurley after 1910 (although it did purchase some Gurley Explorer's Solar Transits for use in Alaska).

According to Gurley and a number of surveyor testimonials, the Jones Latitude Arc meaningfully improved the accuracy and efficiency of a Gurley Solar Transit. The Jones Latitude Arc was a VERY expensive add-on, however, typically adding about 33% to the cost of a Gurley Solar Transit. This likely explains why Gurley did not sell many solar transits equipped with the Jones Latitude Arc, and why these transits are so rarely found today.

The Gurley Light Mountain transit (Serial Number 13474) offered here was made in 1913 (based on the first two digits of the serial number), and reflects all of the little developments that Gurley evolved over the years to perfect its extremely successful solar transit.

The box is unfortunately not original to the instrument. The box contains a different serial number - 9800. Fortunately the box was made for a Gurley Solar Transit, as the box includes the attachment to secure the Burt solar unit. The box also comes with a leather case, which is nice.

I see only two other minor imperfections with this instrument. There is a small amount of wear showing on the outer edge of the horizontal plate, as you can see in the large pic above and in the 360 degree spinner view. Also, the Burt Solar Unit has a slight bit of play in it - like it needs a very thin spacer so that it can rotate and hold its position better.

Gurley Solar Transits come up for sale occasionally. Nice ones sell in the $2500 to $3000 range. Gurley Solar Transits with a Jones Latitude Arc rarely are offered for sale. I am aware of three sales - (i) a nice example sold in 2008 for $5000 plus a 20% commission (Brunk Auction Sale), (ii) a 2012 ebay offering for a damaged instrument that was bid to $4300, and (iii) a private sale of for $4500.

The Beautifully restored Gurley Solar Transit with Jones Latitude Arc offered here is simply breathtaking, and will likely be the featured instrument in any display of fine instruments.

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