Hair, cotton, fibres of organic origin, and feathers arc the best materials, 1 bough fine sawdust and cork powder have been used. Clay with fibres, and fibres with cow-dung have also been employed. The materials should first be powdered, and afterwards applied in the form of washes to the surface, which must be quite free from grease. A covering of canvas, wire netting, hoop iron, boards, etc., should be placed outside.