Figure 34. — 18th-century semicircumferentor. Inscribed brass plate is mounted 

 on a mahogany block; brass sighting bars are mounted on a swivelling bar. 

 The trough compass is on a silvered dial. In collection of the writer. 



wood, is in The Farmer's Museum at Cooperstown, New York. 

 The wood is ash or oak, 12^^ in. long and 6% in. in diameter, with 

 the sighting bars 5 in. high. The compass card consists of cut-out 

 printed letters pasted upon a printed compass rose, and the fleur- 

 de-lis at North is inked-in by hand. This may be a homemade 

 replacement of the original card. The instrument is believed to 

 date between 1760-1775. 



Of equal interest is a large semicircumferentor made by an 

 unknown American instrument maker in the second half of the 

 18th century. The instrument (fig. 34) consists of a plate of 

 hammered brass attached to a quarter circle block of mahogany, 

 with a glass covered trough compass within a silvered opening, and 

 the gradations stamped into the brass. The brass sighting bars 

 are attached to a swivelling bar that can be fixed in place with a 

 set screw underneath the block. The instrument, which is in the 

 collection of the writer, is not signed with a maker's name. Its 

 workmanship is excellent, and professional. 



On the basis of a comparison of these instruments with those 

 produced by known professional makers, it becomes apparent that 

 all of them were made professionally. The possibility that some 

 of these wooden surveying compasses may have been produced by 

 the farmer or local surveyor for his own use is extremely unlikely. 

 Homemade instruments such as those described below were un- 

 questionably the exception instead of the rule. 



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