take them apart; the main study of the progressive paint-maker of to-day is synthetic chemistry—that is, combining separate sub- stances into new forms. Chemistry can tell things that may have been used in making a paint; it can foretell some phenomena that it may develop, but it cannot at all surely predict its "vis viva"—that is, what the stuff will do, and what it will do is the only true measure of its value or worth. "Chemistry is the science of affinity."—(Simon.) "Essentially hetero- geneous bodies excite chemical affinity." Do you fancy that a chemist can probably know the affinities that exist in the kinds of gross matter used by the paint-maker  as well as the paint-maker can? The solids and liquids used to secure a worthy paint must have a liking  for  one  another,  else  you  cannot  get    fairly    homogeneous    liquid   mass;