The air tanks were refilled, and after sailing along on the surface for an hour or two, the submarine was again sent below, as Captain Weston sighted through his telescope the smoke of a distant steamer.
"As long as it isn't the Wonder, we're all right," said Tom. "Still, we don't want to answer a lot of questions about ourselves and our object."
"No. I fancy the Wonder will give up the search," remarked the captain, as the Advance was sinking to the depths.
"We must be getting pretty near to the end of our search ourselves," ventured the young inventor.
"We are within five hundred miles of the intersection of the forty-fifth parallel and the twenty-seventh meridian, east from Washington," said the captain. "That's as near as I could locate the wreck. Once we reach that point we will have to search about under water, for I don't fancy the other divers left any buoys to mark the spot."
It was two days later, after uneventful sailing, partly on the surface, and partly submerged, that Captain Weston, taking a noon observation, announced:
"Well, we're here!"
"Do you mean at the wreck?" asked Mr. Swift eagerly.
"We're at the place where she is supposed to lie, in about two miles of water," replied the captain. "We are quite a distance off the coast of Uruguay, about opposite the harbor of Rio de La Plata. From now on we shall have to nose about under water, and trust to luck."
With her air tanks filled to their capacity, and Tom having seen that the oxygen machine and other apparatus was in perfect working order, the submarine was sent below on her search. Though they were in the neighborhood of the wreck, the adventurers might still have to do considerable searching before locating it. Lower and lower they sank into the depths of the sea, down and down, until they were deeper than they had ever gone before. The pressure was tremendous, but the steel sides of the Advance withstood it.