Not many years ago, there was being erected across the St. Lawrence River a huge bridge, with the largest single span in the world, which it was believed would be not only the largest but the strongest and most enduring structure of its kind in existence. It was being built under the supervision of one of the leading bridge engineers of the world; its design was of an approved type, which had long been standard in the Western Hemisphere; and the steelwork was being fabricated in one of the best equipped bridge works in the country. Nevertheless, when one great cantilever was about completed, and before any live load had been placed on it, the structure collapsed under its own weight. One of the principal members--a massive steel column, five feet square and sixty feet long--crumpled up as though it had been a boy's tin whistle, and allowed the whole bridge to fall into the St. Lawrence, carrying eighty men to their death! The disaster was traced to a very insignificant cause--the failure of some small angle-bars, 3½ inches in width, by which the parts of the massive member were held in place. No engineer had suspected that danger lurked in these little angle-bars. Had the accident happened to a bridge of moderate size, the lessons of the failure would have been noted by the engineers and contractors; it would have formed the subject, possibly, of a paper before some engineering society, and the warning would have had results merely local and temporary. But the failure of this monumental structure, with a loss of life so appalling, gave to the disaster a world-wide notoriety. It became the subject of a searching enquiry by a highly expert board; the unsuspected danger which lurked in the existing and generally approved methods of building up massive steel columns was acknowledged; and safer rules of construction were adopted. It took the Baltimore conflagration to teach us the strong and weak points of our much-vaunted systems of fireproof construction. Only when San Francisco, after repeated warnings, had seen the whole of its business section shaken down and ravaged by fire, did she set about the construction of a city that would be proof against fire and earthquake. It was the spectacle of maimed and dying passengers being slowly burned to death in the wreckage of colliding wooden cars, that led to the abolition of the heating stove and the oil lamp; and it was the risk of fire, coupled with the shocking injuries due to splintering of wooden cars, that brought in the era of the electrically lighted, strong, and incombustible steel car.