Houghton Copy Theodolate, unsigned, circa 1740. Several examples of this type of instrument have turned up, unsigned, to avoid litigation with the original Rowland Houghton Theodolate patented in Massachusetts in 1735. This example is all original except for the sight vanes, which are correct period replacements. The delicate, curvilinear alidade is quite distinctive and the needle is original to this instrument with very delicate North and South crossbar indicators on the needle, typical of this early colonial period. The horizontal circle is graduated beginning with 00, typical to the Boston area makers of this period. (Greenough, etc.) What is unusual is, instead of going from 0 – 90 in each quadrant, this instrument is graduated 00 – 45 – 00 in each of the four quadrants. The replacement display Jacob's Staff Adapter is non-rotating. Horizontal plate, 6 1/2 inches in diameter, 8 3/8 inch alidade, 4 7/8 inch needle.