Figure 81. — Brass surveying compass marked "Rittenhouse & Evans," about 

 1780. Over-all length, 13% in.; diameter of dial, 5/4 in. This instrument, 

 made about 1780, was owned and used by John Johnson in 1818 for surveying 

 the boundaries between Canada and Maine. USNM 309543. 



of Col. Bouchette, finished running the exploring line to the Beaver or Metis 

 River. . . . 



Gift of John Johnson Allen of Burlington, Vt., in 1927. USNM 

 309543. Figure 81. 



Thompson, Captain Samuel Rowland (1 8th century) ; Lewes, Del. 

 Octant made of dark wood and with lignum vitae; brass fittings. 

 This harbormaster's instrument, used by Captain Thompson during 

 the second half of the 18th century, is without numerical designa- 

 tions on the arc. The eighth part of a circle is connected to an apex 

 by two side pieces with a swinging arm hinged at the apex, with a 

 blade at its end that moves along a checkered scale on the arc. 



Gift of George Andrews Thompson of Baltimore, Md., in 1926. 

 USNM 308473. 



VoiGHT, Henry (1738-1814), Philadelphia, Pa. 

 Equal Altitude Telescope of brass, 17 in. long, on wooden tripod 

 about 46 in. high. Objective lens is missing. Signed "Henry 

 Voigt." Made about 1790 and used for determining meridian 

 lines and time observation of the sun's noon transit. This form of 



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