Product Description
This is a most unusual device from the manufacturer W & L. E. Gurley of Troy, NY. It is a very precise rotary table with an dual optical pick-off. A special split-field microscope reads opposite sides of a very accurate glass scale housed in the circular compartment beneath the rectangular 'U-shaped' upper frame.
Gurley is one of the earliest and most well-respected U.S. manufacturers of surveying equipment and this device reflects the high quality for which the firm is known. Similar to a high-end optical theodolite, the microscope is able to read the rotation of the central fixture (about 4 inches in diameter) to an accuracy of 1 second of arc. Gurley received a patent for the readout system used in this device. By taking simultaneous readings on opposite sides of the scale the effects of very minor eccentricities of the scale to the rotation axis are to a great degree nulled.
The U-system holding the microscope is 7 inches wide. The table has a post of 0.625 inch diameter that extends on the underside of the system to a distance of 1 inch. The table is equipped with a clamp system with a micrometer adjustment screw for extremely fine positioning capability.
The system is housed in a very heavy duty wood cabinet of excellent construction. Both the instrument and the cabinet are in exceptionally fine condition. The illumination system for the scale requires a small 3v supply, not included (simple batteries will do). There are a couple of xerox copies included with the instrument, one on the theory of operation, and the other instructions for taking a reading through the microscope. One extra lamp is included. This is very uncommon instrument that probably dates from the 1960's, possibly a bit more recent.
Photo set 1750