"Just what I thought you'd say. No doubt that puddled core will help to hold the huge mass of earth that we're going to dump around it. But we're working that piling in and making the core for another purpose also. With a huge body of water in this hollow there'll be a certain amount of soaking into the subsoil--seepage we call it. It might loosen the ground underneath our dam, and so cause the thing to burst; but with a 40-foot trench, filled with a puddled core which'll stop any water, and this extra 40 feet of piling--just 80 feet of material altogether--we stop that seepage, and at the same time kind of fix a tooth into the ground that'll hold the weight of New York city." The whole thing was gigantic, or, rather, the scheme of it all; for the reader must realize that Jim and his friend were looking down upon an unfinished undertaking. But those smoking engines and the army of men at work were an indication of the enormous labour and skill required in the erection of this Gatun dam, itself only one item in the numerous works of the canal, though, to be sure, one of the vastest. In fact, When Jim learned that from base to summit the dam would measure no less than 135 feet, and would be 50 feet above the level of the water in Gatun Lake, there was no wonder that he gasped. "It just makes a man scratch his head," laughed Phineas. "And sometimes it makes one inclined to swear, for there's folks in the States who can't cotton to what we're doing here, and who wonder why there are so many men employed and so much money being spent. They seem to think that the canal ought to be finished in a matter of three or four years." "Then the sooner they come out here and see for themselves what is happening the better for everyone," cried Jim indignantly. "That dam alone will take a vast amount of time, I imagine." "Then you come along down here, sir, and I'll show you a work that's just as gigantic." Phineas took our hero to the western end of the trench across which the dam would lie, and there caused him more astonishment. For here another army of labourers was employed in delving, while enormous steam diggers tore huge mouthfuls of earth and rock away from the sides of the cutting that was being made to accommodate the double line of three locks which, when America has completed her self-imposed undertaking, will raise the biggest vessel ever thought of to the surface of the lake above, or will drop her with equal facility down on to the bosom of the Atlantic. "There's those steam navvies," observed Phineas, halting in front of one and surveying it reflectively. "A man who runs a machine like that can earn good dollars, and there's competition for the post. Say, Jim, how'd you care to try your hand at it?"