Over thirty miles away at the southern extremity of the Culebra Cut the vessel in transit will be lowered from the high-level lake 30 feet down to the surface of another artificial lake much smaller in content, held at a surface-height of 55 feet above sea-level. These are the single-step duplicate locks known as the Pedro Miguel or "Peter Magill." The construction of these locks required 770,000 cubic yards of cement. On the west side of these locks is the other dam which, with the mighty Gatun dam at the other end, holds up the waters of Lake Gatun. This smaller dam is also of earth, and is about 1,400 feet long and 40 feet wide at the top. It is subjected to a maximum "head" of water of 40 feet, but the average is from 25 to 30 feet. The length of the lake, which is known by the pretty name of "Miraflores," between the Peter Magill and the next set of locks, is about 2,000 yards, and the lake itself covers about 1,200 acres. Its waters are held up at 55 feet above sea-level by two dams at the Miraflores locks. These are the third and last set of locks for a ship proceeding from the Atlantic to the Pacific. They are in two steps, or, to use the more technical expression, "two in flight," and they drop the vessel from the Miraflores Lake at 55 feet elevation down to sea-level. It must be noticed, however, that the fluctuations in the tide of the Pacific end are about 20 feet, and that the height of the lake is given for mean tide. In other words low water during "spring" tides is 10 feet below the average sea-level. The maximum lift for these locks therefore will be 65 feet. There are two dams holding up the waters of the Miraflores Lake, one to the west of earth, and one to the east of concrete. The former is 2,300 feet long and 40 feet wide at the top. The average "head" to which it is subjected is 30 feet, the maximum 40. Its construction is similar to that at Gatun. The concrete dam is about 500 feet long, and is provided with regulating works similar to and of the same dimensions as those at Gatun, the crest in this instance being 39 feet above mean tide-level, with seven openings, allowing a discharge of 7,500 cubic feet per second. The locks themselves will require 1,312,000 cubic feet of concrete. I should add that these dams at Pedro Miguel and Miraflores are, unlike their big brother at Gatun, founded upon the solid bedrock. There has, therefore, been no question as to their permanence and stability. Moreover, as will have been noticed, the pressure of water is only about a half of that at Gatun.