The Soap-Cup Shaving Mug: Water and Soap in One Vessel

"Our invention consists in combining a soap-receptacle with a mug, so that the soap may always be in a convenient position ready for use during the operation of shaving." "And it will be seen that hot water placed in the portion A of the mug, being partially covered over by the bottom of the receptacle B, will not become cooled so rapidly as would be the case if its entire surface were exposed to the air." "A shaving-mug formed as above described need occupy no more space than an ordinary mug, while it possesses the advantage of two receptacles, for water and soap, combined in one, it being merely necessary to dip the brush from one to the other".

Take two tin cans, a tall one for the mug and a shorter one. Cut the short can down to 3 cm deep and cut it in half across its diameter, leaving three tabs 1 cm long on its curved edge. File every cut edge smooth. Set the half-cup inside the rim of the tall can, curved side against the wall, so its bottom sits about 3 cm below the rim and covers part of the water surface. Bend the tabs out over the rim with the pliers to hold it. Put a piece of bar soap in the cup. Fill the mug to just below the soap cup with water from the kettle. Read the temperature every 5 minutes for 15 minutes. Take the cup out, refill the mug with water at the same starting temperature, and read it again. Compare both runs with the notebook.

**George P. Brooks and James McGrady** of Boston received US 66,788, dated 16 July 1867. They wrote that the mug "may be constructed of earthenware, metal, or other suitable material, and the water may be heated in it, instead of in a separate vessel, if desired". **Honest limits.** The notebook splits heat loss into a top share and the rest, and treats the covered part as losing nothing. Real cups still pass some heat through their bottoms. The rates are examples. Your two runs of temperatures are the measurement.