BATTLING WITH THE PANAMA SLIDES 



145 



of the canal. At one time Cucaracha 

 picked up a steam shovel, track and all, 

 and moved it 50 feet away, but still 

 standing ready for operation as though 

 nothing had happened, except that it was 

 cut off from the dirt-train tracks. At 

 another place and time Mohammed did 

 not have to go to the mountain, for it 

 came to him ; so at Panama a shovel was 

 able to make a hundred trips or more 

 back and forth along the base of a slide 

 without moving a step closer to the dirt, 

 for the slide came down just as fast as 

 the shovel worked. 



During their history the Culebra Cut 

 slides destroyed over 200 miles of rail- 

 road track. Sometimes a slide would 

 come down, forcing one track out of po- 

 sition, passing under the next one with- 

 out disturbing it at all, and then upheav- 

 ing the material under the third track 

 mayhap as much as 10 or 20 feet. 



All manner of efforts were put forth 

 to prevent slides. It was once proposed 

 that cutting off the top of the bank above 

 the cut would prevent those that devel- 

 oped through structural breaks. But this 

 work was vigorously prosecuted for 

 awhile with no important bearing on the 

 ultimate result. At another time it was 

 suggested that a revetment of concrete 

 along the banks of the cut would protect 

 it, but this was a failure also. The water 

 that seeped down from the surface got 

 in behind the concrete and caused it to 

 loosen its hold and scale off. 



At another time it was suggested that 

 letting water into the cut would tend to 

 develop an equilibrium and thus prevent 

 additional slides. But this method of 

 treatment succeeded no better than those 

 methods which were tried out before ; 

 and so the settled policy became one of 

 inviting all slides that intended to come 

 down to do so quickly, so as to have it all 

 over with. 



WHAT CAUSES THE SUDES 



The causes of the slides at Panama 

 must be traced to the geologic history of 

 the Isthmus. There are 11 groups of 

 bedded rock and six of igneous rock on 

 the canal line. The two oldest rocks are 

 the Bas Obispo formation and the Las 

 Cascadas agglomerate. Neither contains 



any fossil remains, and so their age can- 

 not be fixed with any degree of definite- 

 ness. The Bas Obispo formation is of 

 volcanic origin and crops out at Bas 

 Obispo, Miraflores, and Old Panama. 

 The Las Cascadas agglomerate is made 

 up of basalt breccia, cemented together 

 with volcanic clay and tufa and other 

 lava flows. 



Culebra Cut contains fossils of sea- 

 living animals, thus proving, along with 

 other evidence, that this great barrier 

 which has stood between man and his 

 dream for more than four centuries was 

 once at the bottom of the sea. 



It is stated that Gold and Contractor's 

 hills, which now stand as the huge posts 

 of the Panama Gateway, are composed 

 of comparatively young volcanic rock 

 blown up to a height some 300 feet or 

 more above their present summits, and 

 that they settled down to their existing 

 level soon thereafter. The evidence of 

 the rocks of the Isthmus is that there 

 were two eras of volcanic activity, the 

 one of terrific force and the other much 

 more gentle, with a long quiescent period 

 between them. 



During the first volcanic era islands 

 arose in the shallow ocean that linked the 

 Atlantic and the Pacific. During the 

 second period the whole land arose and 

 the rivers became active, assorting the 

 rocks as they hurried to the sea. The 

 original bed of the Chagres at Gatun, as 

 it existed then, is now 375 feet below sea- 

 level. After this the ground sank to 8 

 feet below its present level on the Atlan- 

 tic side and to 25 feet below its present 

 level on the Pacific side. This level seems 

 to have been maintained until a time ap- 

 proximating the dawn of the Christian 

 era, when it rose to the present level. 



Interesting proof of this is afforded 

 some 80 miles from Ancon. The Indians 

 there have been using the contents of a 

 shell mound, found at the base of a 75- 

 foot hill, for burning lime. The plain 

 here is about 25 feet above sea-level. 

 The mound contains many varieties of 

 shells and much broken crockery, indi- 

 cating that it was once used as a kitchen 

 midden. About 2 inches of soil cover 

 these deposits, and near-by is a place 

 which shows that it was used as a canoe 



