The early estimates made by the American engineers were far too low, but the French experience had taught the United States to expect such an outcome. Indeed, it is doubtful if anybody believed that the first estimates would not be doubled or quadrupled before the canal was finished. [Illustration: Signature of George Goethals _Chairman and Chief Engineer_] [Illustration: A STREET IN THE CITY OF PANAMA] The journey of the U. S. S. _Oregon_ around the Horn from Pacific waters to the theater of the War with Spain in the Caribbean, in 1898, impressed upon the American public the necessity of building the canal as a measure of national defense. Commercial interests long had been convinced of its necessity as a factor in both national and international trade, and, when it was realized that the _Oregon_ would have saved 8,000 miles if there had been a canal at Panama, the American mind was made up. It determined that the canal should be built, whatever the cost. From the very first there was never any question that the necessary money would be forthcoming. It is a fact unprecedented in all parliamentary history that all of the appropriations necessary for the construction and completion of the Isthmian waterway were made by Congress without a word of serious protest. During the same War with Spain that convinced the United States that the canal must be built, a long forward step was taken in the science of medicine as concerned with the prevention and control of tropical diseases. The theory that yellow fever was transmitted by mosquitoes had been proved by a Cuban physician, Dr. Carlos Finley, a score of years earlier. An Englishman, Sir Patrick Manson, had first shown that disease might be transmitted by the bites of insects, and another Englishman, Maj. Roland Ross, had shown that malaria was conveyed by mosquitoes. It remained, however, for American army surgeons to demonstrate, as they did in Cuba, that yellow fever was transmissible only by mosquitoes of the stegomyia variety and by no other means whatsoever.