Civil War Captain Fields Improved US Parallel Ruler / Sold

Civil War Era Captain Fields Improved Parallel Ruler - Made of boxwood and brass.  Navigators use parallel rulers for laying off a specific course on a chart. They were first invented in 1584 by a Frenchman named Mordente, but only became common in navigation in the 18th century. Captain Feild's (or Field's) design had one of its outer edges divided into degrees like a protractor, with the opposite edge divided into points, half-points and quarter-points (of the compass). This made it easier to read off the bearing of a line than with a plain parallel rule, which had to be moved across the chart to the nearest compass diagram. This example has the inscription: "CAPTN. FIELD'S IMPROVED" and is labeled "USS HARTFORD".  Measures approximately 12 1/8" in length and 2 1/2" wide. 

Inventory Number: MIS 011 / Sold