The German Verein zur Bedförderung des Gewerbefleisses offers the following, among other prizes, for essays on technical subjects: One thousand marks (£50) for a comparative examination of the various methods hitherto used for determination of the hardness of metals, with an exposition of their sources of error and limits of accuracy. It is stated, as a reason for offering the prize, that the methods for making the required tests are but yet little developed, and that no thorough comparison has yet been made of the various methods. The hardness of metals and alloys being a very important factor in several processes, a really good method of determination is highly desirable. Three thousand marks (£150) for the best essay on the resistance to pressure of iron work in buildings, at increased temperatures. It appears that after a certain fire in a manufactory at Berlin, the police authorities issued notices concerning the use of cast-iron columns in high buildings, and that these notices encountered great opposition in many quarters, as it was considered that neither practice nor theory had yet shown any proof that cast iron is less trustworthy than wrought iron in cases of fire.
A brilliant black varnish for iron, stone, or wood can be made by thoroughly incorporating ivory black with common shellac varnish. The mixture should be laid on very thin. But ordinary coal tar varnish will serve the same purpose in most cases quite as well, and it is not nearly so expensive.