THE PANAMA CANAL 



187 



upper and two at the lower end of each 

 of the uppermost locks in each flight. 



In addition a chain device is used to 

 guard the barrier gates against accident, 

 and so controlled as to be capable of 

 checking a ship of 10,000 tons moving 

 at the rate of about five miles an hour. 



More than 95 per cent of the vessels 

 navigating the high seas are less than 

 600 feet in length, and this has been 

 taken as the determining factor for the 

 location of intermediate gates, which are 

 introduced in the design to save both 

 time and water. For the protection of 

 the intermediate gates against vessels 

 using a smaller length of chamber a 

 chain barrier is to be installed. 



Guide piers are provided both up- 

 stream and down, to which vessels will 

 tie before entering the locks. Designs 

 for electric towing machines are being 

 prepared, which will be used for towing 

 vessels into and controlling their passage 

 through the locks by means of lines or 

 cables attached to what may be con- 

 sidered the four corners of the ship. 



Even with all of these precautions ac- 

 cidents may happen, and emergency 

 dams are provided at the head of each 

 flight of locks, consisting of swing 

 bridges, which can be thrown across the 

 locks in case of an accident which 

 makes a connection between the top level 

 and the level below ; wicket girders are 

 let down from these swing bridges, sup- 

 ported by a sill at the bottom and the 

 horizontal truss work of the bridge at 

 the top. These wicket girders act as 

 runways for gates, which are lowered 

 and gradually stop the flow. 



GATUN LAKE WILL STORE WATER EOR THE 

 DRY SEASON 



It will not be out of place at this point 

 to give consideration in a general way to 

 the question of adequacy of the water 

 supply to maintain a large commerce 

 through the locks. Data bearing on the 

 subject have been collected for many 

 years and studied with care. During 

 eight or nine months of the year there 

 is more than a sufficient supply for all 

 purposes, but during the other four or 



three months there is practically none, 

 and it becomes necessary to store a suffi- 

 cient quantity during the rainy season 

 to supply the needs during the dry sea- 

 son. 



The enormous reservoir of Gatun 

 Lake is available for this purpose. The 

 bottom of the canal in the summit level 

 is at reference 40, and it is evident that 

 navigation, with the extreme depths pro- 

 vided of 40 feet in sea water, can be 

 carried on until the surface of the lake 

 falls to reference 8if. As the water sur- 

 face in the lake is to be allowed to rise 

 to reference 87, there is stored available 

 for the dry season a little more than 

 five feet. 



Making due allowances for power 

 consumption, evaporation, about which 

 data are available, seepage and leakage 

 at the gates during a dry season of 

 minimum flow, assumed as following a 

 wet season of minimum flow, an average 

 of 41 passages of the canal per day is 

 possible, using the full length of lock. 

 In the average dry season 58 complete 

 transits of the canal are possible, or a 

 greater number than the 24 hours of the 

 day would permit, allowing vessels to fol- 

 low each other at intervals of one hour. 



With the design for the locks as 

 adopted a certain amount of water can 

 be saved at each lockage whenever a 

 vessel does not draw the full permissible 

 depth of 40 feet by cross-filling or 

 emptying through the middle wall. As 

 a consequence it can be stated that there 

 will be sufficient water for as many lock- 

 ages as the time in the day will permit. 



INGENIOUS METHODS LOR HANDLING THE 

 ROCK AND CEMENT 



At Gatun three locks in flight over- 

 come the difference in level between the 

 lake and sea, and are being constructed 

 in a cutting made through a hill. The 

 excavation, consisting of upwards of 

 5,000,000 cubic yards, mostly rock, is 

 practically completed. The locks are of 

 concrete, and contain about 2,046,100 

 cubic yards of this material. On Janu- 

 ary 1 last they were 49 per cent com- 

 pleted. 



