The tools required would be a small rotary cutter, a sheet-iron box with sliding front and chimney at top. an iron tray, two large ring gas burners, knives or spatulas, and iron moulds shaped like the blocks required. The rubber may be cut in the rotary machine, mixed with powdered sulphur, placed on the iron tray in the sheet-iron box, and heated by the burners. A thermometer hung in the box very close to the iron tray will show the temperature, which must not rise above 300'F. When the rubber is softened, the moulds may be heated in the box, the rubber put in, and the tops of the moulds forced down so as to compress the rubber; the moulds may then be allowed to become cold, and the blocks withdrawn. Before pressing in the rubber, rub powdered French chalk over the insides of the moulds.