little value unless "the results obtained by the method selected will be in harmony with long-time service tests." It is easy to test the water-proofing quality of a dried coating of paint, but such a test determines nothing more than the ability of the paint to exclude water from the surface underneath it. It is easy to test the effect of artificial heat upon dried paint, but this does not determine the power of the paint to withstand sunshine. We have found no quick test to determine the probable life of paint, under given conditions, but are led to conclude that one intimately acquainted with the properties of the subject-matter, and with the forces of nature, may reasonably predict its life, if he knows the method of application, the conditions under which it is to be exposed, and the condition of the surface upon which it is to be applied.