THE PANAMA ROUTE FOR A SHIP CANAL. 265 



show that the maximum discharge in 1879 might have been at the rate 

 of 136,000 cu. ft. per second. As a matter of fact the total channel 

 section in that year was less than it is at the present time. Hence 

 if it be assumed that a flood of 140,000 cu. ft. per second must be con- 

 trolled an error on the safe side will be committed. Other great floods 

 of which there are reliable records are as follows : 



1885 — Height at Bohio 33.8 ft. above low water. 

 1888 — Height at Bohio 34.7 ft. above low water. 

 1890 — Height at Bohio 32.1 ft. above low water. 

 1893 — Height at Bohio 2S.5 ft. above low water. 



The maximum measured rate of the 1890 flood was 74,998 cu. ft. 

 per second, and that of 1893, 48,975 cu. ft. per second. It is clear 

 therefore that a flood flow of 75,000 cu. ft. per second is very rare, and 

 that a flood of 140,000 cu. ft. per second exceeds that of which we have 

 any record for practically forty years. 



It is obvious that the dam, as designed by the commission, is of 

 such a character that no water must be permitted to flow over its crest, 

 or even in immediate proximity to the downstream embankment. In- 

 deed it is not intended by the Commission that there shall be any waste 

 way or discharge anywhere near the dam. At a point about three 

 miles southwest of the site of the dam at Bohio is a low saddle or notch 

 in the hills near the headwaters of a small stream called the Gigante 

 River. The elevation of this saddle or notch is such that a solid 

 masonry weir with a crest 2,000 ft. long may readily be constructed 

 with its foundation on bed rock without deep excavation. This struc- 

 ture is called the Gigante Spillway, and all surplus flood waters from 

 the Chagres would flow over it. The waters discharged would flow 

 down to and through some large marshes, one called Pena Blanca and 

 another Agua Clara before rejoining the Chagres. Inasmuch as the 

 canal line runs just easterly of those marshes it would be necessary to 

 protect it with the levees or embankments to which allusion has already 

 been made. These embankments are neither much extended nor very 

 costly for such a project. The protection of the canal would be 

 further aided by a short artificial channel between the two marshes, 

 Pena Blanca and Agua Clara, for which provision is made in the 

 estimates of the commission. After the surplus waters from the 

 Gigante Spillway pass these marshes they again enter the Chagres 

 River or flow over the low, half-submerged country along its borders, 

 and thence through its mouth to the sea near the town of Chagres about 

 six miles northwest of Gatun. 



The masonry crest of the Gigante Spillway would be placed at an 

 elevation of 85 ft. above the sea, identically the same as that which may 

 be called the normal summit level of the canal. It is estimated that the 

 total uses of water in the canal added to the loss by evaporation taken 



