Mr. John Newman, in his admirable treatise on “Earthwork Slips and Subsidences upon Public Works,” classifies and enumerates slips as follows: Natural causes, 7. Artificial causes, 31. Additional causes due to impounded water, 7. After describing each cause he presents 39 different means used to prevent such slips and describes methods of making repairs. Mr. Wm. L. Strange has had such a large and valuable experience and has set forth so carefully and lucidly both the principles and practice of earth dam construction, that the writer takes pleasure in again quoting him on the subject of _drainage_, of which he is an ardent advocate. He says that, thorough drainage of the base of a dam is a matter of vital necessity, for notwithstanding all precautions, some water will certainly pass through the puddle. It is at the junction of the dam with the ground that the maximum amount of leakage may be expected. The percolating water should be gotten out as quickly as possible. The whole method of dealing with slips may be summed up in one word–_drainage_. The proper presentation of these two phases of our subject would in itself require a volume. The interested reader is therefore referred to the different authorities and writers cited in Appendix II. Jerome Park Reservoir Embankments. The Jerome Park reservoir is an artificial basin involving the excavation and removal of large quantities of soil, and the erection of long embankments with masonry core walls, partly founded on rock and partly on sand. The plan and specifications call for an embankment 20 ft. wide on top, with both slopes 2 on 1, and provide for lining the inner slope with brick or stone laid in concrete, and for covering the bottom with concrete laid on good earth compacted by rolling. [Illustration: Section at Sta. 99.] [Illustration: Section at Sta. 76+20. FIG. 20.–GRAPHICAL EXHIBIT OF STUDIES OF JEROME PARK RESERVOIR EMBANKMENT.] Wherever bed rock was not considered too deep below the surface the core walls were built upon it. In other places the foundation was placed 8 to 10 ft. below the bottom of the reservoir and rested upon the sand. It appears that the plans of the Jerome Park embankment were changed from their original design, prior to the report of the board of experts, on account of two alleged defects, namely, “cracks in the core wall” and “foundation of quicksand,” and incidentally on account of the supposed instability of the inner bank. In describing the materials on which these embankments rest the experts remarked that all these fine sands are unstable when mechanically agitated in an excess of water, and that they all settle in a firm and compact mass under the water when the agitation ceases. That they are quite unlike the true quicksands whose particles are of impalpable fineness and which are “quick” or unstable under water.