Heavy slide as canal bank caves. For 500 feet along the Welland Ship canal earth slid into the manmade ditch yesterday as shown in this photograph. About 34,000 cubic yards of earth fell in the first disturbance since 1935. Shipping was not impeded by the slide. The minor avalanche was attributed by the engineering staff to natural erosion. Dredges will clear the debris shortly. Grading of the banks at tremendous cost would be the only means of eliminating them, the engineers stated. A slide occurred several years ago near the scene of yesterday's slip.