ings; e.g., a paint made from white lead and linseed oil when properly applied to a sound surface cannot be expected to protect it, under fair conditions, more than five or six years, whereas a paint made from a good natural iron oxide and the same oil, applied to a like surface under similar conditions, will protect it easily twice as long. The observer will note this if he will recall his observations of the durability of paint made from ordinary mineral colors on barns or freight cars, as compared with the more delicate tints used on houses and more elaborate structures.

Another feature of interest pertaining to inert pigments is, that where the same liquids are used with them for the paint for each coating applied, the observer finds that the dried paint seldom cracks, peels, or blisters, and  if  it  does  the  inference  should  be