Up to June 30, 1939, toll-paying traffic (of 300 or more net tons Panama canal measurement) transiting the canal had aggregated 104,417 vessels, of 624,968,699 gross registered tons, 469,241,390 Panama canal net tons; tolls paid amounted to total transit revenue to $458,574,500.46; net canal transit ex penses to $206,966,555.41; and net revenue (surplus) to $251, The transit revenues for the years 1915 and 1916 were considerably reduced by "slides" which closed the canal to traffic for a portion of each year. For the four years ending June 30, 1939, ships of 34 nationalities passed through the canal; American ships were slightly over 32% of the total, British slightly over 24%. About 25% of the cargo was in the United States inter-coastal trade. Of the 1939 traffic 9,011,267 cargo tons passed from the Atlantic to the Pacific and 18,855,360 cargo tons passed from the Pacific to the Atlantic.
Naval and other vessels owned and operated in the Government service of the United States and Panama, war vessels of Co lombia, and vessels which are sent through the canal solely for repair at the Balboa shops are exempt from the payment of tolls, and such vessels are omitted from the statistics in the above table. From the opening of the canal on Aug. 15, 1914, to June 30, 1939, they numbered Io,i i 1, the majority of them being American Naval vessels or Army transports.
The following is the saving in nautical miles effected by the Panama canal in length of all-water routes between certain European and Atlantic-Gulf ports of the United States and vari ous Pacific ports: Early Interest in an Isthmian Canal.—When Columbus crossed the Atlantic, the object he had in view was to find a west ern passage from Europe to Cathay. It was with the greatest re luctance and after many years of unremitting search that early explorers became convinced that the two American continents formed a continuous barrier to the Far East. The question of creating an interoceanic waterway was raised immediately. In 1523 Charles V of Spain initiated the movement to build a canal, and four years later directed Hernando de la Soma to explore the Rio Grande and Chagres river on the Isthmus. In 1529 Alvaro de Saavedra, a lieutenant of Vasco Nunez de Balboa, completed plans for the construction of a canal, but he died before his plans could be submitted to the king of Spain. The possibility of constructing a canal across the Isthmus of Tehuantepec was suggested by Her nando Cortez after his conquest of Mexico, and Spanish explorers in Nicaragua reported the possibility of cutting a canal through Nicaragua and utilizing the waters of the large Lake Nicaragua.
In 1534 Charles V ordered the governor of the region of Panama to make surveys of a canal along the Chagres river, following more or less the present canal route. This was done, but the governor sent a discouraging report. Antonio Galvao, a Portuguese naviga tor, published a book in 1550 in which he claimed that a canal could be cut at Tehuantepec, Nicaragua, Panama or Darien, and in 1551 the Spanish historian F. L. de Gomara submitted a memorial to the king of Spain urging that the project be undertaken im mediately. When Philip II succeeded Charles V to the throne he became interested for a time in the construction of a canal and directed a survey of the Nicaraguan route but no effort was made to follow the plans, for Philip foresaw the possibility of trouble with other European powers if an interoceanic waterway were opened through the Spanish possessions in the New World to the Far East. This policy of Philip II was maintained by the Spanish Government for nearly two centuries after his death, and it was not until the latter part of the 18th century that the question was revived and the Spanish Government ordered surveys made of the Tehuantepec and Nicaragua routes. However, political disturb ances in Europe prevented further action at that time. The project was given great stimulus early in the 19th century when Baron von Humboldt, famous geographer, returned to Europe from a trip to Central and South America and reported the possibility of a canal along several routes between Mexico and Colombia. His writings were widely read in England, France, Spain, and the United States. In 1814 the Spanish Cortes adopted a formal decree for the construction of an Isthmian canal and authorized the formation of a company to undertake the work, but no substantial results were accomplished and within another decade all of the Spanish colonies in Central and South America had established their independence and the possibility of Spain taking part in the great project faded. In 1825 the Republic of the Centre, having received applications for concessions from citizens of Great Brit ain and from citizens of the United States, made overtures to the United States Government for aid in constructing a canal. From that time until the construction of the canal was begun in 1904 the question was debated in practically every session of the Congress of the United States. Also, numerous concessions were granted to citizens of the United States, France, and Belgium, both for the Nicaragua and Panama lines, but with the exception of the con cession of 1878 for Panama and that of 1887 for Nicaragua, no work of construction was done under any of them.