THE TANGLED MAZE OF STEEL SKELETONS THAT ARE A LOCK IN THE MAKING
The ship then is in the lowest lock, one pair of gates closed tightly behind her. Another pair confronts her holding back the water in the lock above, which if filled, will be just 281⁄3 feet above the surface of that on which she floats. But the water about her is now slowly rising. Another set of electric motors concealed in the concrete wall have set in motion the valves in the floor of the lock, and the water is flowing in from the tunnels, raising the ship and at the same time lowering the water in the lock above. When the vessel’s keel is higher than the sill of the lock above the upper gates swing slowly back and fold in flat with the wall. The ship is now in a chamber 2000 feet long filled to a level. The locomotives pull her forward a thousand feet or so. Again great gates close behind her. Again the water rises slowly about her lifting her with it. The first process is repeated and she enters the third lock. By the time she has been drawn out into the lake and the locomotives have cast her off, more than 100 electric motors with a horse power ranging from 71⁄2 to 50 each will have contributed to her progress. Altogether over 1000 individual motors will be required for the different locks. Indeed the whole interior of those massive lock walls is penetrated by lighted galleries strung with insulated wires bearing a death-dealing current. Men will be stationed at the various machinery rooms, but the whole line of machinery can be operated from a central operating tower on the lock above.
CHAPTER XI
GATUN LAKE AND THE CHAGRES RIVER
That section of the Canal, which for the convenience of engineering records and directions is known as the Central Division, comprises within its boundaries two of the great spectacular features of the Isthmus—Gatun Lake and the Culebra Cut. I have already described the scenic characteristics of this lake, but some discussion of the part it plays in the economy of the Canal will not be out of place.
In the first place the creation of the lake depended on the type of canal to be selected. A sea-level canal could not exist with the lake; a lock canal could not have been built without it. The meanderings of the Chagres, crossing and recrossing the only practicable line for the Canal, and its passionate outbursts in the rainy season made it an impossible obstacle to a sea-level canal, and all the plans for a canal of that type contemplated damming the stream at some point above Gatun—at Bohio, Gamboa or Alhajuela—and diverting its outflow into the Pacific. On the other hand the lock canal could not be built without some great reservoir of water to repeatedly fill its locks, and to supply the waterpower whereby to operate them. Hence Gatun Lake was essential to the type of canal we adopted.
The lay reader will probably be surprised when he hears how carefully the area of the Chagres watershed and the average rainfall were studied, and the height of the dam and the spillway adjusted to make certain a sufficient supply of water for the locks. The only locks with which these could be compared are those at the “Soo”, or outlet of Lake Superior. That canal, the busiest one in the world for eight months in the year, averaged 39 lockages a day during that period on the American side and a smaller number through the Canadian locks. The water in Gatun Lake will be sufficient for 41 passages, if the full length of the locks is used or 58 if only the partial length is used, which will be the case with steamships of less than 15,000 tons—and in ships of this class the bulk of the world’s trade is conducted. If the limit of 41 lockages seems low, it must be remembered that time is quite as much a factor in the case as is the water supply. It will take an hour and a half to put a ship through the locks. That time therefore technically constitutes a “passage”. In the 24 hours there would be 36 passages possible, and under the circumstances that would draw most heavily on the lake there will be water enough for 41.
