A cement made as follows may be used with great success, both for covering pulleys with leather and on belt joints before riveting. The leather will tear before coming off, if carefully done. Make an extract by digesting 1 part of coarsely crushed nut-galls with 8 parts of rainwater, let stand for several hours, and filter through linen. Then pour 1 part of cold water over 1 part of best glue, let it stand for twenty-four hours, and heat to make a concentrated glue solution. To use the above, warm the nut gall extract, and coat the leather with it. Warm the pulley, which should be roughened, and coat with the glue. Lay the leather on the warm pulley, press firmly together, binding it tightly with cord.