268 POPULAR SCIENCE MONTHLY. 



After leaving Bohio- Lake, at Obispo, a flight of two locks is found 

 at Pedro Miguel, about 7.9 miles from the former or 21.5 miles from 

 Bohio. These locks have a total ordinary maximum lift of 60 ft., 

 divided into two lifts of 30 ft. each. The fifth and last lock on the 

 route is at Miraflores. The average elevation of water between Pedro 

 Miguel and Miraflores is 30 ft. above mean sea-level. Inasmuch as the 

 range of tide between high and low in Panama Bay is about 20 ft. the 

 maximum lift at Miraflores is 40 ft. and the minimum about 20. The 

 twin locks at Miraflores bring the canal surface down to the Pacific 

 Ocean level, the distance from those locks to the six-fathom curve in 

 Panama Bay being 8.45 miles. There are therefore five locks on the 

 Panama route, all arranged on the twin plan, and, as on the Nicaragua 

 route, all are founded on rock. 



Near Obispo a pair of guard gates are arranged ' so that if it should 

 become necessary to draw off the water from the summit cut the level of 

 Lake Bohio would not be affected.' 



An unprecedented concentration of heavy cutting is found between 

 Obispo and Pedro Miguel. This is practically one cut although the 

 northwesterly end toward Obispo is called the Emperador while the 

 deepest part at the other end, about three miles from Pedro Miguel, 

 is the great Culebra cut with a maximum depth on the center line of 

 the canal of 286 ft. On page 93 of the Isthmian Canal Commission's 

 report is the following reference to the material in this cut : 



There is a little very hard rock at the eastern end of this section, and 

 the western two miles are in ordinary materials. The remainder consists of a 

 hard indurated clay, with some softer material at the top and some strata and 

 dikes of hard rock. In fixing the price it has been rated as soft rock, but it 

 must be given slopes equivalent to those in earth. This cut has been estimated 

 on the basis of a bottom width of 150 feet, with side slopes of one on one. 



When the old Panama Canal Company began its excavation in this cut 

 considerable difficulty was experienced by the slipping of the material 

 outside of the limits of the cut into the excavation, and the marks of 

 that action can be seen plainly at the present time. This experience 

 has given an impression that much of the material in this cut is un- 

 stable, but that impression is erroneous. The clay which slipped in the 

 early days of the work was not drained, and like wet clay in numerous 

 places in this country it slipped clown into the excavation. This ma- 

 terial is now drained and is perfectly stable. There is no reason to 

 anticipate any future difficulty if reasonable conditions of drainage are 

 maintained. The high faces of the cut will probably weather to some 

 extent, although experience with such clay faces on the isthmus, indi- 

 cates that the amount of such action will be small. As a matter of fact 

 the material in which the Culebra cut is made is stable and will give no 

 sensible difficultv in maintenance. 



( To be continued. ) 



