and to better the appearance of surfaces to which they are applied.

In Oil Paints of value the end aimed at is a close union of solids or pigment and liquids or binder, that is, we take inorganic solid matter in a finely divided state and mix with it organic liquid matter, and then try to link them together either mechanically or chemically. Ordinary mechanical mixtures in which the solids and liquids have little or no affinity for each other, or in which the powders are feebly suspended in the liquid, scarcely deserve the name of paint.

The essentials of a preservative and protective covering for structural steel may be stated as follows:

I. Mechanical Properties. That it must work properly, that is, offer but a slight resistance to the stroke of  the  brush,