Description and Notes:
The production name of this device is Sphinx section liner, but the title of the original patent is Parallel Ruler, which, as stamped on the left bottom of the base plate, was issued on July 14, 1891 with US patent number 455,779, and the corresponding current U.S. Class is 33/447 (Geometrical Instruments. Straightedge type. Base attached. Set shift, postively).
This type of section liner had been produced by a number of instrument makers, such as F. Weber & Co., Keuffel & Esser, and Eugene Dietzgen. The maker's signature on the presented one is unfortunately ruined by a later drilled recess pin hole for fixing it onto a drawing board or drafting table, but it is clear that the company was located at Fulton Street, New York. This device is made of cherry wood (the ruler blade is ebonized cherry) and steel, and is in perfect working order. In addition, it appears to be a rare early example of its kind because it has a sliding type adjustable stopping bar instead of a cam shaped rotating one as proposed in a later issued patent (669,239).
The function of this section liner is the same as that of the Riefler's. However it relies on a relatively simpler thumb activated friction drive mechanism to achieve equal spaced forward movement of the inclined ruler, and it can be used for drawing either left or right inclined parallel lines. As shown in the above picture, the assembly of the inclination angle adjustable ruler blade is attached to a steel rod which can be slide along and rotated about the base plate. The left end of the rod is passing through a level which is initially secured to the right side of the left most support of the rod due to spring force. By pressing the lower end of the level, it would produce a wrench about the rod and the contact friction of the two would force the rod to advance a preset distance defined by the stopping bar. When released, the level will be pushed back to its initial position by the spring, but the rod will remain on the advanced position due to the friction force produced by the spring activated locking clamp at the left end of the base plate. The advancement of the rod can be repeated until the lower joint of the ruler blade assembly touched the right support of the rod. Finally, by pressing the locking clamp to the right to release the clamping force, the rod can be pushed back to the starting position.