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The National Geographic Magazine 



up to the greatest flood height, after 

 which the rate of discharge over the 

 spillway would decrease. This regula- 

 tion of the Chagres floods, therefore, 

 takes care of itself. It requires no at- 

 tention. After discharging over the 

 spillway, the flood waters would flow 

 through an artificial channel down into 

 the Chagres River beyond any of the 

 canal works and where no damage would 

 be done. 



About 10 miles up the Chagres from 

 Obispo at a point called Alhajuela there 

 is an excellent site for a dam. It has 

 been proposed to build at this Alhajuela 

 site a great masonry dam for the pur- 

 pose of impounding flood waters of the 

 Chagres River to the extent of the stor- 

 age capacity behind the dam, and so re- 

 duce the flood effects in Take Bohio. 

 This storage reservoir would also act as 

 a source of feed water for the canal 

 should the traffic on it in the future be- 

 come so large as to require this addi- 

 tional supply. 



THE CULEBRA CUT 



From Obispo, 30 miles from Colon, 

 the canal line runs toward the southeast 

 through the continental divide in a di- 

 rect course toward Panama, and for 

 nearly 7 miles from Obispo a great cut 

 has to be made through the high ground 

 forming that divide. For a distance of 

 about 5 miles from Obispo this is known 

 as the Emperador Cut, beyond which 

 lies a mile and a half known as the Cu- 

 lebra Cut. The greatest depth of this 

 cut at Culebra is about 250 feet, and the 

 amount of material to be removed in this 

 stretch of 7 miles of canal excavation is 

 about 43,000,000 cubic yards. It is the 

 greatest single feature of the entire canal 

 construction. 



The summit or Bohio Lake level ends 

 at a point called Pedro Miguel, about 

 1 y 2 miles southeasterly of the Culebra 

 Cut and 38 miles from Colon, where is 

 located a flight of two locks arranged in 

 twin plan like the others, each one of 



the pair having a lift varying from 27 

 to 31 feet, according to the varying 

 height of water in Lake Bohio. By 

 means of these two locks the water sur- 

 face in the canal is brought down to an 

 elevation about 28 feet above sea level. 

 The last lock on the line is at a point 

 called Miraflores, a little less than a 

 mile and a half from the Pedro Miguel 

 locks. From Miraflores to the end of 

 the canal, at a point called La Boca on 

 the Bay of Panama, is less than 5 miles, 

 and this portion of the canal constitutes 

 what may be called the Pacific section 

 or level. The water of this Pacific sec- 

 tion of the canal rises and falls coinci- 

 dently with the tides in the Bay of Pan- 

 ama, and as the range of tide in that 

 bay is about 20 feet, the Miraflores lock 

 is largely a tidal lock. Its minimum 

 lift, therefore, at high tide, is 18 feet, 

 while the maximum lift at low tide is 38 

 feet. It is obvious from these tidal con- 

 ditions that if the canal were constructed 

 as a sea-level canal a tidal lock would 

 be needed at or near its Pacific end. 

 That part of the canal line between 

 Miraflores and the Bay of Panama is 

 located closely along the course of the 

 Rio Grande, which is mainly a tidal 

 river, its two principal tributaries above 

 Miraflores being Rio Pedro Miguel and 

 Rio Caimitillo, both being small and in- 

 significant streams. 



The length of canal between the shore 

 lines is about 44 miles, although the 

 length between the 6-fathom curves on 

 the two sides of the Isthmus, as has al- 

 ready been stated , is 49 miles, 1 3 of which 

 lie in the artificial Lake Bohio. The 

 creation of Lake Bohio would necessi- 

 tate the relocation and rebuilding of the 

 railroad between Bohio and Obispo, 

 throwing it back upon higher ground. 



No canal with locks can be operated 

 without provision for the water used in 

 taking boats through the locks, for 

 evaporation, for seepage, and for other 

 purposes incident to maintenance and 

 operation of the canal. At each lock- 



