Here as elsewhere it is possible to give only a very general idea of the difficulties which were encountered and overcome in the course of construction. The drainage of the "Cut" during the work was in itself a heavy and important task. It was necessary to keep out the water of the surrounding country and to rid the excavated area of water collecting in it. A system of diversion channels, carrying off the Obispo River and its tributaries, effected the first object, and the second problem was solved by gravity drains and pumps. On the whole, this mighty trench through the isthmian hills is not only the biggest thing to the credit of a nation which delights in bigness, but the greatest achievement of its kind the world has ever seen. FOOTNOTES: [16] "South America," p. 26. CHAPTER XIII. THE LOCKS. The Panama Canal belongs to the "age of concrete." All other vast works of construction, such as the Pyramids of antiquity and the Assouan Dam of to-day, have been built of live natural rock. At Panama everything--locks, wharves, piers, breakwaters--has been constructed of concrete. The Americans have not only built these incomparable piles of masonry; they have manufactured the material out of which they are built. This circumstance makes the rapid completion of the canal all the more wonderful. Not less than four and a half million cubic yards of artificial stone have been produced for the built portions of the canal and its accessories. This amount of concrete, we are informed, would make an ordinary sidewalk nine feet wide by six inches thick reaching more than twice round the earth. The broken stone which is one of the ingredients of concrete was quarried and transported from Porto Bello--a name famous in the annals of West Indian romance--20 miles to the east of Colon; while the sand came mostly from Nombre de Dios, also a celebrated place 20 miles further to the east, the Atlantic terminal of the old paved trans-isthmian road along which the Spanish mule convoys brought the silver of the Incas from Panama. Millions of yards of stone came from Porto Bello. Hundreds of bargeloads of sand came from Nombre de Dios and from islands in the Atlantic and Pacific. Myriads of barrels of cement were shipped from the United States to Cristobal, an outskirt of Colon, thence carried by barges to Gatun or by railway to the Pedro Miguel and Miraflores lock sites. Dozens of mighty "mixers" were ready to receive these diverse materials. Each of these could accommodate ten tons of sand, cement, crushed stones, and water. This indigestible mixture the machine would toss and churn round for a minute or so in its interior and then belch it all out in the shape of unhardened artificial stone.