While Tom and Mr. Damon continued on to Atlantis after the oil, the young inventor lamenting¹ from time to time that his remarks about the real destination of the Advance had been overheard by Mr. Berg, the latter and his companion were hastening back along the path that ran on one side of the sand dunes².  
"What's your hurry?" asked Mr. Maxwell, who was with the submarine agent. "You turned around as if you were shot when you saw that man and the lad. There didn't appear to be any cause for such a hurry. From what I could hear they were talking about a submarine. You're in the same business. You might be friends."
 
"Yes, we might," admitted Mr. Berg with a peculiar³ smile; "but, unless I'm very much mistaken, we're going to be rivals."
 
"Rivals? What do you mean?"
 
"I can't tell you now. Perhaps I may later. But if you don't mind, walk a little faster, please. I want to get to a long-distance telephone."
 
"What for?"
 
"I have just overheard something that I wish to communicate to my employers, Bentley & Eagert."
 
"Overheard something? I don't see what it could be, unless that lad—"
 
"You'll learn in good time," went on the submarine agent. "But I must telephone at once."
 
A little later the two men had reached a trolley⁴ line that ran into Atlantis, and they arrived at the city before Mr. Damon and Tom got there, as the latter had to go by a circuitous⁵ route. Mr. Berg lost no time in calling up his firm by telephone.
 
"I have had another talk with Mr. Swift," he reported to Mr. Bentley, who came to the instrument in Philadelphia.
 
"Well, what does he say?" was the impatient question. "I can't understand his not wanting to try for the Government prize. It is astonishing. You said you were going to discover the reason, Mr. Berg, but you haven't done so."
 
"I have."
 
"What is it?"
 
"Well, the reason Mr. Swift and his son don't care to try for the fifty thousand dollar prize is that they are after one of three hundred thousand dollars."
 
"Three hundred thousand dollars!" cried Mr. Bentley. "What government is going to offer such a prize as that for submarines, when they are getting almost as common as airships? We ought to have a try for that ourselves. What government is it?"
 
"No government at all. But I think we ought to have a try for it, Mr. Bentley."
 
"Explain."
 
"Well, I have just learned, most accidentally, that the Swifts are going after sunken treasure—three hundred thousand dollars in gold bullion⁶."
 
"Sunken treasure? Where?
 
"I don't know exactly, but off the coast of Uruguay," and Mr. Berg rapidly related what he had overheard Tom tell Mr. Damon. Mr. Bentley was much excited and impatient for more details, but his agent could not give them to him.
 
"Well," concluded the senior member of the firm of submarine boat builders, "if the Swifts are going after treasure, so can we. Come to Philadelphia at once, Mr. Berg, and we'll talk this matter over. There is no time to lose. We can afford to forego the Government prize for the chance of getting a much larger one. We have as much right to search for the sunken gold as the Swifts have. Come here at once, and we will make our plans."
 
"All right," agreed the agent with a smile as he hung up the receiver. "I guess," he murmured to himself, "that you won't be so high and mighty⁷ with me after this, Tom Swift. We'll see who has the best boat, after all. We'll have a contest and a competition, but not for a government prize. It will be for the sunken gold............