The canal has a summit elevation of 85 feet above the sea, reached by
a flight of three locks located at Gatun, on the Atlantic side, and by
one lock at Pedro Miguel and a flight of two at Miraflores, on the
Pacific side; all these locks are in duplicate--that is, two chambers,
side by side. Each lock has a usable length of 1,000 feet and a width
of 110 feet. The summit level is maintained by a large dam at Gatun
and a small one at Pedro Miguel, between which is the great Gatun
Lake, with an area of 164.23 square miles. A small lake, about two
square miles in area, with a surface elevation of 55 feet, is formed
on the Pacific side, between Pedro Miguel and Miraflores, the valley
of the Rio Grande being closed by a small dam and the locks at
Miraflores.