The Ruler Letter Scale: A Ruler That Weighs With Its Own Weight

"C represents a slide, moving in the channel A′, and retained in place by the frame or plate B. The slide consists of an angular block, having its short arm a to protrude beyond the short plate B, and which will form the fulcrum of the scale." "The rule is to be placed in the position shown in fig. 4, that is, with the slide underneath, and the weighing end to project over the end of a table, desk, or other resting place. The letter may be held by its flap catching in the hook, or may be pierced in one corner by the pin."

**Plate.** Weigh the ruler on the kitchen scale and run the notebook with its mass and length. Cut a strip of aluminium sheet 15 × 2 cm and file notches in one edge at the notebook's distances from the letter end. **Slide.** Cut a small angular block from hardwood block with a short arm that sticks out below the ruler as the fulcrum. Tape the plate along the ruler's top so the slide runs under its notched edge and clicks into each notch. **Hook.** Screw a strip of spring steel along the ruler's end with its tip bent into a hook, to hold a letter by its flap. **Test.** Set the slide at the half-ounce notch, lay the ruler over the edge of the table with the slide on the edge, and hang letters weighed on the kitchen scale. Note which tip the ruler and which balance, and compare with their weights.

**T. Grow Taylor** of Lawrenceville, St. Lawrence County, New York, signed US 69,948 on 13 April 1867; it is dated 15 October 1867 and antedated 17 April 1867. (The specification prints his name as T. Grow Taylor; the drawing sheet's header reads J. G. Taylor. Which initial is right is not settled here.) His inner notch marked half an ounce and the next a full ounce, the notches could be cut in the channel instead of a plate, and he offered gum or a pin in place of the hook. **Honest limits.** A taped aluminium plate, a hardwood slide and a spring-steel hook stand in for his fitted parts. The notebook ignores the hook's weight; the ruler's mass and length are examples. Your weighings are the result.