12 CAULKING AND PACKING MATERIALS, PREPARED BUILDING STONES, ARTIFICIAL BUILDING STONES, LIME, PLASTER, PIPE INSULATING COVERINGS, ASPHALT ROOFING, PORTABLE HOUSES, AND ASBESTOS BUILDING MATERIALS-NAMELY, SHINGLES, WRAPPINGS, WALL BOARDS, AND THE LIKE, BUILDING AND PORTLAND CEMENT, POROUS BUILDING STONES IN ALL FORMS