The great blot on the high-level scheme is that the great Gatun dam is not founded on solid rock. The Gamboa dam of the tide-level project would have been founded throughout on hard rock, from which it could have been built up of masonry so that the structure should be part and parcel of the rocky framework of the globe itself. The Gatun dam as recommended in the minority report, on the other hand, was designed to consist essentially of a mass of earth dumped upon an alluvial plain so as to fill up a gap of 2,000 yards between two ranges of hills, the gap through which the Chagres escapes to the Atlantic. Thus the Gatun lake was to be held up as a glacier lake is held by a moraine blocking a valley. We shall presently describe the high-level canal as it is to be, from which it will be seen that it will provide a magnificent waterway, but before concluding the present section I must mention the special point in which it will be inferior to a tide-level canal. This is for purposes of defence. A fortress has to be preserved from capture, but not from damage. The locks, however, must be preserved from serious damage, which demands far more elaborate protection. Such protection, moreover, has to be provided at two positions (Gatun and Milaflores) about 30 miles apart. _The High-level Canal as it is to be._ The Spooner Act, the law under which the Canal is being constructed, enacts that it shall be "of sufficient capacity and depth as shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use, and such as may reasonably be expected." Accordingly the following dimensions have been selected:-- 1. A minimum depth of 41 feet. The Suez Canal has a depth of 31 feet[10] admitting of the passage of ships with a draft of 27 feet.[11] The channel of this canal is now being deepened, so that by 1915 it is hoped that a depth of 36 feet[12] will be obtained. The Kiel Canal has a depth of 30 feet. The average draft of the Cunard s.s. _Mauretania_, the largest ship now afloat, is about 32 feet, but she is stated to draw, when fully laden, about 37 feet, and there are comparatively few harbours in the world which she could enter fully loaded. [10] Report, Board of Consulting Engineers, p. 175. [11] "Four Centuries of the Panama Canal," p. 436. [12] _Daily Telegraph_, June 18, 1908. 2. A minimum bottom width of 200 feet in the Culebra Cut. The minimum bottom width, or width at a depth of 31 feet, in the Suez Canal is 108 feet. The bottom width of the Kiel Canal is 72 feet.[13] [13] Report, Board of Consulting Engineers, p. 173. 3. Each lock will have a usable length of 1,000 feet and a width of 110 feet. The locks of the Kiel Canal have an available length of 492 feet and width of 82 feet. The _Mauretania_ has a length of 790 feet and beam of 88 feet.