We work upon the theory that the paint used for priming naked steel should be of a preservative nature, i.e., of such a nature that it will not only possess the power to inhibit the corrosion of the metal but also the power absolutely to exclude air and water from the metal, and that the finishing or top coats should be of a protective nature, that is, of such nature that they will protect the primer or bottoming paint from the action of rainfall, sunshine, and other external deteriorating conditions. As the first or prime coat must form a receptive foundation that will be able to hold all subsequent or protective coatings both on and up, it should be largely formed of basic materials, so composed as to secure on the surface of the metal a firm and unyielding coating of an elastic, durable, cohesive, and adhesive  cement;  it  is  probably  necessary