Such a phenomenon would not be so startling in mere magnitude as the slides which added so greatly to the work of the engineers on the Canal, and made tourists, wise with the ripe fruits of five days’ observation, wag their heads knowingly when Col. Goethals calmly repeated his assertion that the water would be turned in by August. The Colonel, however, had not withdrawn or even modified this prophecy so late as June 10, 1913. Despite the almost daily news of increased activity of the slides he clung with tenacity to his purpose of putting a ship through in October. [Illustration: _Courtesy of Scientific American_ THE ORIGINAL CULEBRA SLIDE A Y. M. C. A. club had to be moved to escape this slide which in 1913 was still moving] If these slides were an entirely new and unexpected development for which no allowance of either time or money had been made in the estimates of the Canal builders they would of course justify the apprehension they have awakened in the non-professional mind. But the slides were in fact anticipated. The first slide recorded during our work on the Isthmus was in 1905; the others have only been bigger, and have been bigger only because the Canal being dug deeper has weakened the bases of even bigger hills along the banks. All the same, the proportions of the slides are terrifying and the chief geologist declared that they would not cease until the angle of the Canal bank became so gentle that gravity would not pull the crest down. The slides are of two sorts. The simpler is a mere swift rush of all the loose surface dirt, sand, gravel and stone down the surface of the bank. These gravity slides, mere dirt avalanches, though troublesome, present no new problems. To stop them it is necessary only to carry the crest of the bank further back so that the angle will be less steep. But the great, troublesome slides are those caused by the pressure of the hill-top on its undermined and weakened base. These originate at the top of the hill, making their presence known by gaping fissures opening in the earth and extending in lines roughly parallel to the Canal. Once started the whole mass, acres in extent, moves slowly toward the cavity of the Canal, three feet a day being its swiftest recorded progress. At Culebra the slides compelled the moving of a large part of the town away from the edge of the Cut, lest it be swept into the gorge. The Culebra Y. M. C. A. clubhouse, the largest on the Zone had to be torn down to escape this peril.