Primitive methods of grinding -- The bell mill or coffee mill -- Disc mills -- Disintegrators -- Carr’s disintegrator -- Carter’s disintegrator -- Adjustment of disintegrators -- The Williams pulveriser -- Myrobalans and Valonia crushers -- Sawing mills -- Shaving mills -- Dyewood cutting machines -- Screening of ground materials -- Hatching of bark -- Disintegrators and fire insurance -- Dust from disintegrators -- Chain conveyors -- Belt conveyors -- Vibrating conveyors PAGE 316 CHAPTER XXII. _THE EXTRACTION OF TANNING MATERIALS, AND THE MAKING OF EXTRACTS._ Leaching -- Early forms of leaches -- The press-leach system -- Handling of liquors -- Distributing troughs and valves -- Construction of leaches -- Influence of temperature -- Use of silent boiling jet -- Closed extractors -- Sprinkling leaches -- Manufacture of extracts -- Decolorisation of extracts -- Soluble extracts -- Concentration of extracts -- Yaryan evaporator -- Multiple effects -- The use of extracts in the tannery -- Effect of temperature on extraction and colour PAGE 328 CHAPTER XXIII. _FATS, SOAPS, OILS AND WAXES._ Characteristics of fats and oils -- Chemical constitution -- Nature and production of soaps -- Insoluble soaps -- Distillation of fats -- Solvents of oils -- Drying oils -- Saturated fatty acids -- Non-drying liquid fatty acids -- Less-saturated liquid fatty acids -- Castor oil -- Tallow -- Neatsfoot oil -- Wool fat -- Holden fat -- Distilled wool grease -- Distilled stearine -- Olive oil -- Castor oil -- Turkey-red oil -- Linseed oil -- Boiled oils -- Japan for leather -- Cottonseed oil -- Sesame oil -- Cod oil -- Shark liver oil -- Whale oil -- Seal oil -- Menhaden oil -- Fish oils -- Fish tallow -- Dégras and Sod oil -- Waxes -- Sperm oil -- Beeswax -- Carnauba wax -- Japan wax -- Volatile or essential oils -- Birch oil -- Wintergreen oil -- Mineral oils and waxes -- Vaseline and vaseline oil -- Paraffin wax -- Ozokerit -- Resin oils -- Resin PAGE 350 CHAPTER XXIV. _OIL TANNAGES, AND THE USE OF OILS AND FATS IN CURRYING._ Primitive use of oil in leather manufacture -- Chamoising and the production of washleather -- Manufacture of Moellon, or Dégras -- Sod oil -- Formaldehyde leathers -- “Crown” and “Helvetia” leathers -- Theory of oil leathers -- Processes of currying -- Theory of the stuffing process -- Hand-stuffing -- Drum-stuffing -- Stuffing of dry leather -- “Spueing” and its causes -- Fat-liquoring PAGE 378 CHAPTER XXV. _DYES AND DYEING._