with powerful 20-inch centrifugal pumps. When at work they steamed up and down the channel, sucking up the mud, and carrying it out to sea.

Another interesting dredge used was the big ladder dredge Corozal. It is a great floating dock, as it were, with a huge endless chain carrying 52 immense, 35-cubic-foot buckets. On the center line amidships there is a large opening down to the water. The big elevator framework carrying the endless chain goes down through this and into the water at a considerable angle. The buckets pass around this, and as they round the end of it their great steel lips dig down into the material until filled, then they come up at the rate of three every five seconds and deposit their burden in a huge hopper which conveys it to the barge at the side of the dredge. The dredge is anchored fast at a given place, and keeps on attacking the material beneath it until the desired level is reached. This dredge, with the sea-going suction dredges, will be retained as the permanent dredging fleet. The stationary suction dredges at the two ends of the canal were used to pump up the soft material and to force it out through long pipe lines into the swamps or into the hydraulic cores of the earth dams.

Several old French ladder dredges were rescued from the jungle and put into commission at the beginning of the work, and they held out faithfully to the end, dividing honors with the newer equipment in hastening the day when the oceans might go inland to Gatun and Miraflores. While they looked like toys beside such giant excavators as the Corozal, they probably showed more

efficiency than any other class of excavators of their period of construction. They were attended by large self-propelling scows built by the French. When these were filled they steamed out to sea and dumped their burden and then steamed back again for another load. Some of the dredges were attended by ordinary barges which were towed out to sea by tugs and dumped.

Another interesting machine used on the Pacific end of the canal was the Lobnitz rock breaker. This consists of a sort of pile driver mounted on a large barge. Instead of a pile driving weight there is a big battering ram made of round steel, pointed at one end. It is lifted up perhaps 10 feet and allowed to drop suddenly. As some of these rams weigh as much as 25 tons their striking force may be imagined. When the ram struck the rock the top would shake back and forth like a bamboo pole, in spite of the fact that it was made of the best steel and more than 15 inches in diameter. Sooner or later the rams would break off at the water line, this being due to the fact that the constant flexion at that point set the molecules in the steel and took away all its elasticity.

It was found desirable to excavate a part of the sea-level channel before the water was let into it. To accomplish this a big dam, or dike, was built across the channel several miles inland, and steam shovels were used behind this dike. As the work neared completion, however, it was found advisable to let the water come further inland, so that the dredges could extend the field of their activities. To do this another dike was thrown across the channel about a mile north of the first one,

and water was admitted to the section of the big ditch between these two dikes. The engineers were afraid to cut a small ditch in the top of the first dike, and allow the water to eat the dam away as it flowed in, for fear that it would rush in so rapidly it would destroy the second dike. Therefore they filled the basin between the two dikes by siphon and by pumping, a process which required the drawing in of billions of gallons of water. This was accomplished in due time, however, and then 16 tons of dynamite was placed in the no longer useful dike. An electric spark did the rest.

The distinguishing features of the ends of the canal are the big breakwaters at Toro Point, at the Atlantic end, and Naos Island, at the Pacific end. The former extends from the shore out into the sea for a distance of 2 miles and has a large lighthouse at the seaward end. It was built by dumping stone from the shore out into the sea, this process being followed by driving piles into the dumped stone and building a railroad on the crest, over which the stone was hauled for its further extension. The top of the breakwater is covered with huge stones weighing from 8 to 20 tons each, these to make sure that it will stand against the pounding of the waves. Two minor breakwaters were also built at the Atlantic end to protect the terminal basin.

The big dike at Naos Island in the Pacific is more than 17,000 feet long and transforms the island into the cape of a small peninsula. There was a threefold purpose in its construction - to cut out the cross currents that brought thousands

of yards of sand and silt into the canal channel, to afford a dumping place for a large quantity of the spoil from Culebra Cut, and to make a connection with the mainland for the fortifications on Naos, Flamenco, and Perico Islands. In building it the engineers were under the necessity of first building a trestle on which the spoil trains could be backed and dumped. The piles had to be driven in soft, blue mud, and as the rock was dumped, it sank down and down until, at places, ten times as much stone was required as would have been necessary if the ocean bottom had been firm. In addition to this thousands of trainloads of material were dumped in the landward end of the dike, some 20,000,000 cubic yards of material being thus disposed of.

The last part of the canal work to be completed will be the terminal facilities at the ends of the big waterway. At the time this book went to press they were something more than a year from completion, but the indications were that they would be finished within the time limit originally set for the completion of the canal itself. These terminal facilities consist of dry docks, wharfage space, storehouses, and everything else necessary to perform any service that might ordinarily be required for passing ships, whether they be those of commerce or of war. The main coaling station is to be established at the Atlantic end. The storehouses, the laundry, the bakery, and the other equipment of the Isthmian Canal Commission and the Panama Railroad also will be made a part of the permanent terminal plant on that side of the Isthmus.