We may now begin to consider the canal as a whole and in its completed state. From deep water in Limon Bay, 41-foot depth at mean tide, to deep water outside Panama, 45-foot depth at mean tide, is just about 50 miles. The greater part of the canal is at high elevation, only 15 miles of it being at sea-level. We shall note the varying depths and widths of the channel when we take our imaginary journey along it. Here it is enough to say that the minimum width will be 300 feet, the minimum depth 41 feet, the breadth and depth being, however, for the greater portion of its course, greater than these dimensions. Its highest point above sea-level, as the reader already knows, is 85 feet--that is, 85 feet at the surface of the water, and 40 feet at the canal bottom. The depth along this stretch is therefore 45 feet. The Panama Canal, though not so long as the Kiel and Suez Canals, is very much broader and deeper. Suez is 108 feet wide and 31 feet deep as _minima_; Kiel, 72 feet and 29-1/2 feet. The Manchester Ship Canal is 120 feet by 26 feet. In length Panama, with its 50 miles, comes third, Suez being 90, Kiel 61, and Manchester 35-1/2 miles long. During the building of the canal the department of construction and engineering was arranged in three divisions--the Atlantic, embracing the engineering construction from deep water in the Caribbean Sea to include the Gatun locks and dam; the central division, extending from Gatun to Pedro Miguel; and the Pacific division, from Pedro Miguel to deep water in the Pacific Ocean. For the ordinary student, however, the channel divides naturally into four sections, the Atlantic level, the lake, the cutting, and the Pacific section (in two levels separated by locks). The invisible channel of the waterway begins at the mouth of Limon Bay, about eight miles from Gatun locks. Limon, also known as Colon or Navy Bay, is about three miles wide and three and a half miles long from north to south. It is shallow, from three to seven fathoms deep, and seems to be steadily growing shallower. This is not surprising, as it is fully exposed to the "northers," which blow with terrific force from the Caribbean, and no doubt carry into the bay a good deal of detritus from the bottom of the sea. The heavy rains of the isthmus must also scour the land perpetually down into the bay. On the east side of the bay is the flat Manzanillo Island, a mile long by three-quarters broad, on which stands the city of Colon. This town, which was once known as Aspinwall, owes its existence to the Panama Railway, of which it is the northern or Caribbean terminus. Its position on the railway gave it an advantage over the old town of Chagres, a little distance along the coast to the west, which, though once a flourishing port, has now fallen on evil days. Near Colon is Cristobal, the new Atlantic terminal of the canal. [Illustration: Gatun Upper Lock, looking North from Lighthouse.]