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 REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 57

 The standard bottom width in firm earth, including the dredged portions in soft material between the shore line of Limon Bay and Bohio, was fixed at 150 feet, the side slopes in the same material being taken at one vertical on two horizontal.
 In rock the bottom width was taken at 200 feet with side slopes in the channel of ten vertical on one horizontal, i. e., practically vertical. The side slopes above water, as well as below, in firm earth between Bohio and Obispo and south of Paraiso were taken at the inclination of two vertical on three horizontal.
 Some modifications of these standard sections were made by the Board in its estimates of quantities of material to be excavated in combined rock and earth sections between Bohio and Pedro Miguel, but not including the Culebra section. At many places throughout this distance the lower portions of those parts of the cuts above the water surface in the canal will be rock overlaid by earth or softer material. In the great summit cut the surface material overlying the rock for a considerable distance in the vicinity of Culebra Hill is clay, which, like all clay, slips easily when wet. When, however, this clay is drained, or otherwise protected from becoming saturated, it stands with satisfactory firmness and gives no trouble. Throughout these combined rock and earth slopes the rock is given a face slope in the estimates of ten vertical on one horizontal and the clay or other material above it one vertical on two horizontal. In the great Culebra cut, which really means the summit divide from Obispo to Pedro Miguel, a distance of seven and onefourth miles, a special form of section has been taken, although it includes the same elements of slope adopted for other portions of the cuts taken out in the dry. The same rock section for the prism of 200 feet bottom width and with side slopes of ten vertical on one horizontal is carried up to an elevation of 10 feet above mean tide, at which elevation there is provided a horizontal berm 50 feet in width on each side of the canal prism. From the exterior limits of these berms benches are assumed for the purpose of estimate, each 30 feet high, with a face slope of four vertical on one horizontal, the width of the bench at top being 12k feet. These benches are carried to the upper limit of the rock portion of the cut. This makes the average or mean slope of the rock three vertical on two horizontal. The clay or other soft material overlying the rock is given the same slope of one vertical on two horizontal already described.
 It is believed by the Board that the estimated volume based upon these side slopes is ample. It is probable that large portions of this summit cut, composed of harder rock than the indurated clay which forms the material classified as soft rock, will permit of faces having a slope of four vertical on one horizontal to be taken out much higher than 30 feet. It is further believed that there will be little sliding of these benches, assumed in the computations of quantities, so that the volume taken out of the great summit cut is much more likely to be less than that estimated than in excess of it, especially as a contingent margin has been added to all items of cost.
 The materials classified as soft and hard rock have been exposed with surfaces fully as steep as four vertical on one horizontal ever since the old company ceased work in 1889, a period of sixteen years. Furthermore, these slopes and others equally steep produced by the excavation made by the new French company have been under the personal observation of two members of the Board throughout the past six years, and under the daily observation of another member for over a year. During this time the effects of weathering have been small, soft rock as well as the hard having stood without sensible slipping or other deterioration. In fact, it is the result of extended experience with these steep faces both in Central America and on the Isthmus that the steeper the faces stand without crushing at their lower portions the less weathering and wash from the tropical rains will occur. It is therefore highly desirable to finish these slopes in as high benches and with face slopes as steep as practicable.
 Very few slips of rock have occurred in the deepest portions of the Culebra cut since it was first opened. They are small and have been of such rare occurrence as not to affect the correctness of the preceding observations. The cross sections of the approach channels to be dredged in the harbors of Colon and Panama have been described under "Harbors."
 It is believed by the Board that the cross sections of the prism for all parts of the canal from deep water to deep water are well adapted to meet the requirements of the law under which work