The outside finish of the house should have received as soon as put up the first or priming coat of paint, this is usually done more or less by piecemeal as the different parts of the house are completed, and wall require attention mainly to see that the materials are pure and that the surfaces are well covered. This first coat should contain a large proportion of white lead, which will adhere to the new wood far better than any other substance and will retain the second coat well. Pure linseed oil should be used, but unless care is taken this is likely to be adulterated with fish oil which dries slowly and never hardens like pure oil. The only way to detect the presence of fish oil is by its fishy smell and this is sometimes hard to observe. Linseed oil is also adulterated with oils of resin and pine, and these are very hard to detect, except by long experience.