PROGRESS AT PANAMA. 449 



in opening the Mindi cut is due to the wish to complete the excava- 

 tion of rocks, and thus render submarine blasting unnecessary. Of 

 the eleven dredges at work in this division, four are European, and 

 vary from GO to 180 horse-power ; the remaining seven are American, 

 of 240 horse-power, their maximum capacity of excavation being 6,000 

 cubic metres per day. But repairs to machinery, rains, stoppage dur- 

 ing the extreme heat of the day and at night, and other delays that 

 can not be remedied, have reduced the daily yield to 3,000 cubic 

 metres. 



The level of the remaining bed of the first division is from 4 to 10 

 metres above the sea. Part of a hill near Bohio remains at the eleva- 

 tions of 20 and 28 metres. 



The Chagres is both the upper and the lower limit of the second 

 division, and crosses it seventeen times in its length of 17 kilome- 

 tres. The average level is 12 metres above the sea, except in a sin- 

 gle hill of 25 metres height and in a sudden rise to the same elevation 

 at the end of the division. The excavators are moved on railway- 

 tracks by an engine of 8 to 10 horse-power, and empty their buckets 

 into cars on adjacent rails. Every facility for dredging is presented 

 by the Chagres River, the depth of which is such that dredges can be 

 put at each crossing. 



Just within the third division is the Gamboa hill, where occurred 

 the great explosion of 1886 in honor of M. Ferdinand de Lessejjs. The 

 charge was 8,250 pounds of dynamite and powder, and blew out 30,000 

 cubic metres of material. Farther on is the Corrosita, still 45 metres 

 above the sea. But the most remarkable feature of the division is the 

 great barrage at Gamboa. Its central line will cross the Chagres be- 

 tween the Cerro Obispo and the Cerro Santa Cruz. Its length at the 

 base will be 300 metres, its height 35 metres, and, with a reveted 

 slope of four to one, it will contain 10,000,000 cubic metres of rock 

 and clay. No excavation is needed for the foundation ; a bridge is 

 now building across the valley, and from it trains will discharge into 

 the valley below their loads of rock and earth excavated from the Cor- 

 rosita and neighboring sections. The pressure of water in the basin 

 will seal the dam by forcing the clay into the interstices of the rock- 

 mass, and by deposits brought down by the river. The capacity of 

 the basin will be one billion cubic metres, or double the accumulation 

 of waters during the worst rainy season. Nature has furnished the 

 other walls of this reservoir in the ridges on each side of the Chagres, 

 and in the natural ascent of the valley toward Cruces. The outlet of 

 the basin will be a derivation of the Chagres around the hills of Ba- 

 rucco and Carga-Plata to the bend north of the forty-fourth kilometre ; 

 the outflow will depend upon the height of the water in the basin, but 

 it will never be such that, when coupled even with the drainage of 

 the remaining water-shed of the Upper Chagres, floods can occur in 

 the lower course of the river. 

 VOL. XXXII. — 29 



