The Self-Chalking Line Reel: The Line Comes Out Already Chalked

"The upper end of the staff A is provided with a receptacle, D, for containing pulverized chalk or whiting, and this receptacle is closed by a cap, E, which is connected to the staff by the screw-threaded portion e. An aperture, F, which communicates with the lower end of the receptacle D, and an aperture, G, in the cap E, permit the line H to be unwound from the reel and drawn out through the pulverized chalk." "For describing circular arcs the reel is used in the following manner: A sufficient amount of line is unwound so as to correspond with the radius of the required curve, and the line is wrapped around the staff A so as to prevent the rotation of the reel."

**Staff.** Cut 45 cm of hardwood dowel. Drive a nail into one end and file its head to a point: the foot. **Reel.** Cut two 6 cm plywood discs with the hole saw and glue them to a 3 cm length of dowel as the drum. Mount it on an M6 bolt through the staff 12 cm from the top so it turns freely, glue a short dowel handle into one disc, and wind 10 m of cotton twine on it. **Chalk box.** Cut 8 cm of PVC pipe, glue an end cap on one end and screw it to the top of the staff. Drill a 3 mm hole in its side near the bottom and one in the loose top cap. Thread the line in through the side hole, up through the pipe and out through the cap. Fill the pipe with marking chalk and push the cap on. **Test.** Tap two nails into a wall at the same height 3 m apart. Pull the line out through the chalk, hook it on both nails, pull to 10 N on the spring scale and snap it; then to 30 N and snap again. Stretch a second line as tight as it will go along the same nails and measure how far each chalk mark's middle sits below it. Compare with the notebook and with a bought chalk line.

**James Bathgate** of Cincinnati, Hamilton County, Ohio, received US 70,684, dated 12 November 1867. His reel was journalled between two staffs shod with ferrules; for bricklayers he ran the line through bushed holes in the staff to a ring, and for arcs he wrapped the line round one staff and swung the other. His claim is the reel, chalk receptacle, cap, apertures and line combined. **Honest limits.** A dowel, plywood drum and PVC pipe stand in for his staffs, reel and receptacle, and one staff stands in for two. The notebook treats the line as a shallow sag; its line weight is an example. Your measured sags are the result.