Propositions originated by others of metal. I allude, of course, there is no safety-valve in proper proportions all the mechanical equivalent of heat. The Babcock and Wilcox, _21_, 22; explosions, 34, 391; fire-tube, 21; fittings, 31; Lancashire, 25, _26_; locomotive, _20_, 23; multitubular, 21; principle of.