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Where the cut was not impeded by the slides it looked just like this picture. When the water was let in about nine-tenths of the cut was in this condition

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SLIDES FROM BOTH BANKS BLOCK THE CANAL: SEPTEMBER 20, 1913

"The slides seem to be maneuvered by the hand of some great marshal and sent forth to prey in every way calculated to put the canal enginow they come in the dead of night, neers to discomfiture; now they are quiescent, attempting to lull the engineers into a false security; spreading chaos and disrupting everything in whatever direction they move" (see text, page 133).

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BATTLING WITH THE PANAMA SLIDES

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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. 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 railroad track. Sometimes a slide would come down, forcing one track out of position, passing under the next one without disturbing it at all, and then upheaving 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 developed 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 SLIDES

The causes of the slides at Panama must be traced to the geologic history of the Isthmus. There are II 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

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any fossil remains, and so their age cannot be fixed with any degree of definiteness. 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 sealiving 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.

The

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. original bed of the Chagres at Gatun, as it existed then, is now 375 feet below sealevel. After this the ground sank to 8 feet below its present level on the Atlantic side and to 25 feet below its present level on the Pacific side. This level seems to have been maintained until a time approximating 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 75foot 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, indicating 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

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