31 INDUSTRIAL FILTERING APPARATUS NAMELY, FLUID FILTERS, MICRO-POROUS FILTERS FOR POLISHING LIQUIDS, FILTERS FOR SEPARATING SOLIDS FROM LIQUIDS FILTERS FOR REMOVING ENTRAINED SOLIDS FROM GASES, BACTERIOLOGICAL FILTERS, MICRO-POROUS FILTER CANDLES OF CERAMIC MATERIAL, AND DISCS AND HOLLOW TUBES FORMED OF MICRO-POROUS MATERIAL FOR FILTERING PURPOSES