A. Sea-level section of canal, seven miles long, from Atlantic Ocean to Gatun Locks, where by a series of three locks vessels are raised to Gatun Lake, eighty-five feet above sea level. B. Small area of land dredged away as soon as Gatun Locks were completed. C. Electric towing motor, four of which tow each vessel entirely through the locks. They run on cog rail along the lock walls. D. Lock gate under construction. E. Floor of first lock from Atlantic side. Note holes in floor for admitting the water. F. Lock for vessels coming from Pacific side. G. Base on which concrete posts were erected for electric lights. A row of lights on all sides of the locks making operation at night as safe as day. H. Incline from locks of different levels up and down which the towing motors run on cog rails.] [Illustration: GAILLARD CUT LOOKING SOUTH FROM BEND IN EAST BANK NEAR GAMBOA The train and shovel are standing on the bottom of the cut. The water in the drainage canal is about ten feet below the bottom of the canal, or at elevation +30.] [Illustration: A CYLINDRICAL VALVE MACHINE, MOTOR AND LIMIT SWITCH This machine is one of many which are used to regulate the flow of water to the locks. All valves are controlled from a central operating station on each of the three sets of locks. The limit switch automatically shuts off the power and stops the motor when the valve is entirely open or shut.] [Illustration: CUCARACHA SLIDE ATTACKED BY A FLEET OF DREDGES This great slide was the source of much trouble to the engineers. At one time it entirely blocked the canal at the narrow point shown in this photograph, but the seven dredges of the ladder, suction and dipper type, made short work of cutting the 150-foot channel shown here, and then proceeded with the work of entirely clearing the cut. The view looks north from the slide past Gold and Contractor’s Hills. _Copyright by Underwood & Underwood, N. Y._] [Illustration: STEAM SHOVEL BURIED UNDER FALL OF ROCK] [Illustration: THE GREAT GAILLARD CUT At this point the canal is cut through what is practically a mountain range. The material excavated consisted largely of rock and formed one of the hugest engineering problems in the world’s history. The cut is nine miles long, 300 feet wide, 272 feet greatest depth and required the excavation of 100,000,000 cubic yards of material.]