Barcol hardness test the Barcol impressor was developed by Walter Colman as a hand-held, portable means of assessing the hardness of a material during World War II. The United States Army Air Corps required a hand-held method of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing normal rivets with soft lead or wooden ones which would fail during flight. The impressor operates when the tip is pressed against the material in question. The hardness of the material determines how far the tip indents and this is transferred by a tension spring and lever to be read
Janka Kupala National Theatre donations of citizens. In 1944 has been renamed in honour of classic of the Belarusian literature, poet Janka Kupala. Janka Kupala National Theatre Janka Kupala National Theatre (, Minsk) is the oldest theatre of Belarus. Also, the theatre is an object of cultural heritage of Belarus. The building of the theatre was built in 1890 by the project of architects Konstantin Vvedenski and Korol' Kozlovskiy. The main facade looks out onto the square formed by the intersection of Karl Marx and Engel'sa Street. The theatre was opened on September 14, 1920, and it is located in a building of the