While the great Isthmian highway will be completed far enough ahead to be ready to handle all traffic that offers long before the official opening date, it will, on the other hand, never reach that stage where dredges will not be needed. There are 22 rivers which wend their way from the watersheds of the canal, and pour their loads of sand and silt into it. Of course, these rivers are small--so small, indeed, that few of them would be dignified by being called rivers in the United States. But when the heavens open and the floods descend, as they do so frequently during the rainy season at Panama, these usually quiet, lazy, little streams become almost as angry as the mighty Chagres itself, and they rush down to the canal heavily freighted with sand and silt. If the water in the great interoceanic channel is to be kept at its appointed depth of 41 feet, dredging perforce must be continued from year to year, summer and winter, spring and fall. And so it is that the dredges will be met by every ship that steers its course from Cristobal to Balboa, or from the Atlantic to the Pacific. Few ships large enough to tax the dimensional capacity of the locks ever will go through the canal. Full 90 per cent of all the ships that sail the seas could go through locks one-half the size of those at Panama. So far as commercial shipping is concerned, a 15,000-ton vessel plying tropical waters is considered large, and a 20,000-ton ship is an exception. According to the best shipping authorities, the day when vessels of more than 25,000 tons will find it profitable to ply on the routes which lead through the Panama Canal is so far in the future that they are not able to discern it. With reference to the Navy, naval experts generally agree that the United States will celebrate many a decade of passing years before a battleship too large to use the present lock chambers is a possibility. When a ship makes its maiden voyage through the canal, the measurements to determine its net register will be taken by the shipping experts in the employ of the United States. When this work is completed the master of the ship will be required to pay the toll before he can take his vessel through the canal. If he should fail to pay the toll the vessel itself would be put on the block and sold at auction, if necessary, to reimburse the United States for its passage. However, it is not to be expected that such contingencies as these will arise. When once a ship has been measured, the formality will not have to be gone through with on future visits. It is not expected that each ship will be actually measured for every dimension as it comes to the canal on its first trip, since its net register tonnage probably will have been determined long before, and the canal officials will only check up the work already done elsewhere to assure its accuracy.