Page:Popular Science Monthly Volume 74.djvu/443

Rh careful study of all existing data, on the assumption that the water surface of the lake will have an area of 110 square miles, he gives the following figures:

The water available is estimated at not less than 1,225 cubic feet per second natural flow at Gatun during the three months of lowest river stage, and to this amount there are to be added an additional volume of 1,577 cubic feet per second, resulting from a four feet allowable fluctuation of the lake surface. There are then 2,802 cubic feet per second available, of which the difference between 2,802 and 1,437, or 1,365 cubic feet per second, will be available for lockages. This amount of water, according to General Abbot, will be adequate for 26 daily transits. Should there be need for more stored water, the same can be secured by the construction of a dam at Alhajuela, where sufficient water can be impounded to increase the number of lockages by 40, though only 27 have been assumed by the minority.

It is absolutely certain that there can be no deficiency of water for any conceivable traffic demands.

Since the foregoing estimates were made it has been found that the Gatun Lake will have a surface area of about 164 square miles, instead of 110, as assumed. The lock dimensions have also been increased, as explained, and more water will be required for each transit through the canal. The estimates relating to the available water supply as above quoted therefore need revision.

And thus, in the light of the information then available, the type of the canal was fixed in 1906 by action of the Congress of the United States in substantial conformity with the recommendation of the minority of the board of engineers, and for three years the work of construction has been actively pushed.

The progress that has been made is clearly set forth in the records of work done. Measured by cubic yards of excavation it has been highly satisfactory. The graphical presentation herewith is from a recent summary published by the Engineering News. It appears from the figures compiled for that summary that the total excavation since the canal became the property of the United States at the close of the year 1908, amounted to 59,980,000 cubic yards, of which 53,161,000 cubic yards had been taken out of the canal prism, and 6,819,000 cubic yards were excavated from the locks and spillway sites and from other points outside of the canal proper. Of the total work, that done by steam shovels (work in the dry) amounted to 37,155,000 cubic yards, and dredges had excavated 22,825,000 cubic yards.

It has been estimated by the canal commission that the total excavation to complete the canal on the lines of the accepted project (not including the work by the French canal companies) is 142,000,000 cubic yards. According to these figures there were about 89,000,000 cubic yards yet to be removed from the canal prism on January 1, 1909.