An 850 ft. long steam main working at a pressure of 120 psi ruptured. Two lengths of pipe were submitted for examination, one containing the rupture and the other from an unaffected part removed to facilitate repair. The rupture surfaces were smooth, suggesting that the failure had taken place either at a weld in the pipe or at a discontinuity in the material. Microscopic examination through the joints at the ends of the rupture confirmed that the pipe had been made from strip and the edges lap-welded. The second case concerned an 8 in. diam pipe in which a...