The middle wall is to extend 1,600 feet above the upper gates and below the lower gates as an approach wall against which vessels to be locked may lie while waiting for the gates to open. The side walls will not be as long, and will flare out at their ends. The lock chambers are to be 110 feet wide and 1,000 feet long and will pass vessels of 40 feet maximum draught in sea water. The upper lock in each flight is to be subdivided by additional gates into a 600 foot and a 400 foot lock so that water may not be needlessly wasted in passing small boats. These smaller subdivisions may be used until vessels of over 550 feet length require passage. The lifts will average 28 feet, but will vary with changes in tide, lake level, and conditions of lockage. The diagram below shows the entire lock system at Gatun. [Illustration: Fig. 2.--General Arrangement of the Locks, Valves and Gates at Gatun. S. V., Stoney valve. G. V., Guard valve. E. D. P., Emergency dam pier. U. G. G., Upper guard gate. U. G., Upper gate. M. G., Middle gate. S. G., Safety gate. L. G.--U. L., Lower gate, upper lock. L. L. G.--I. L., Lower gate, intermediate lock. L. G.--L. L., Lower gate, lower lock. L. G. G., Lower guard gate. Ch., Fender chain. Ga., Gauge. L., Ladder. St., Stairs. Inc., Incline. I., Intake. O., Outlet. In each side of the wall Between, there will be A and B-- 3 cylindrical valves. C and D-- 7 cylindrical valves. E and F-- 10 cylindrical valves. G and H-- 10 cylindrical valves. ] Near the bottom of each wall will be a large culvert for passing water from the lakes into the upper chamber, and from chamber to chamber, and then out to the canal below the locks. The intakes (See Fig. 2) will be located at “I” and outlets at “O”. The water enters and leaves the culverts through several small openings, the intakes being screened. The flow of water in the culverts is to be controlled by what is called the Stoney type of valves. These valves occur in pairs which are duplicated at each of the lifts so that if one pair is disabled the other set may be used while repairs are being made. On each side wall, at the middle gates in the upper lock there will be only one set of valves, but none in the middle wall. The flow between the culvert in the middle wall and the lock chamber is to be controlled by cylindrical valves capable of withstanding pressure on both sides. By using these valves water may be saved under certain conditions of lockage by cross-connecting the twin chambers through the middle wall.