This is the Third Technical Progress Report, from the Ship Structure Committee to the convening authority, the Secretary of the Treasury.It continues the series of technical reports which began with the publication of the Final Report of the Ship Structure Committees predecessor, the Board to Investigate the Design and Methods of Construction of Welded Steel Merchant Vessels.This Ship Structure Committee was formed in 1946 for the purpose of prosecuting a research program to improve the hull structures of ships by an extension of knowledge pertaining to design, materials and methods of fabrication. Fractures continue to occur in welded ships built during World War II, and many of these ships are still in use.This has led the Committee to continue to direct the bulk of its effort to the solution of the brittle fracture problem in welded ships.