Patent Model for Parallel Rule and T-Square by Eugene Towne

This instrument has a wooden handle attached by a large brass thumbscrew to a brass protractor that is divided to single degrees and numbered by tens in both directions from 10 to 170. The protractor is screwed to a rectangular brass piece that slides in a groove in a rectangular wooden guide-piece. The guide-piece has brass clamps and thumbscrews for affixing the instrument on a table. The protractor is also attached by a split nut to a metal screw shaft that runs the width of the instrument. A thumb rest and gear on the left clamp rotates the screw shaft.

A T-square is a technical drawing instrument used by draftsmen primarily as a guide for drawing horizontal lines on a drafting table. In this instrument, the two blades of the T-square are not fixed in a perpendicular position but rather can be rotated to any angle on the protractor. The large thumbscrew can then be used as a handle to move the blades along the screw shaft, allowing the user to draw parallel lines.

Eugene James Towne (1847–after 1900) of North Dana, Mass., received a patent for this device in 1877. He submitted this example with his application as a prototype for the instrument, and the U.S. Patent Office marked it on the bottom: 187330 (/) L.1201.1228. Towne, a cabinetmaker, and J. W. Goodman, who made pianos, billiard table legs, and other wooden items in North Dana, apparently intended to manufacture the device together. However, the instrument likely was not widely adopted.

References: Eugene J. Towne, "Improvement in Parallel Rulers" (U.S. Patent 187,330 issued February 13, 1877); Edwin Eugene Towne, ed., The Descendants of William Towne (Newtonville, Mass., 1901), 284; The Worcester County Directory for 1878–79 (Boston: Briggs & Co., 1878), 41; 1870 and 1900 U.S. Census records.

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