MemberMay 6, 2021 at 2:06 am
A nice topographic description of the Suez Isthmus by another 19th-century scholar; Samuel Colcord Bartlett. His account simply and clearly lists in order from Med to Red the border lakes of Egypt, noting they are separated by four ‘sills’ (ridges) across the Isthmus:
Med Sea – Lake Menzaleh [Qantara ridge] Ballah Lakes [El-Gisr] Lake Timsah [Serapeum] Bitter Lakes [Chaloof] Suez Gulf
 The Isthmus of Suez at its narrowest part is seventy miles wide. The canal, indeed, measures one hundred miles (164 kilometres) from Port Said to Suez, but it does not cross the narrowest place nor follow a straight line. Following the line of the canal southward, we pass for many miles through the broad Lake Menzaleh, and reach first a series of sandy downs, the highest point of which is Kantara, “the bridge” between the eastern and the western deserts. Here ran one of the greatest thoroughfares of the world, the highway between Egypt and the East. Passing next the shallow Lake Ballah, we reach El Guisr, the greatest elevation on the isthmus, about ten miles in width, and at its highest point sixty-five feet in height. Then comes Lake Timsah, the “crocodile” lake, midway between the two seas. South of it is the second elevation, the heights of Serapeum, about eight miles broad, and at its  highest point sixty-one feet high. South of this lie the Bitter Lakes, a great depression, extending south-easterly some twenty-two miles in length, and from two and a half to five miles in breadth. Their greatest depth is about thirty-five feet below the sea-level. Before the water was admitted in 1867 by the modern canal, this depression was, and had for ages been, dry. The bottom was covered with a layer or layers of salt of great extent (seven miles by five) and of variable thickness, but reaching the depth of thirty-three feet. Between the Bitter Lakes and the Red Sea lies the third and last barrier, the heights of Chaloof, about five miles broad from north to south, and rising for a short distance twenty feet or more above the sea-level. Then follows the sandy plain of Suez for a distance of about ten miles, rising but a few feet (about four [m] on the average) above the level of the sea.
Bartlett, Samuel C. From Egypt to Palestine Through Sinai, the Wilderness and the South Country. New York, NY: Harper, 1879.
Note that the Bitter Lakes lie between the Serapeum ridge and the Chaloof. The Bitter Lakes depression in the 19th century was around 10 m deep (30+ feet) but actually deeper because of the thick salt pan on the bottom which has probably now long dissolved by the ingress of water in the Suez Canal. The Great Bitter Lake is the deepest of the border lakes, large and deep enough to drown an army in turbulent conditions.