“So do I,” assented Tom.  “But even with the one we have I’d take a chance and look for the underground city.”

“I’ll mail the letter,” went on Mr. Damon, who was as eager over the prospective adventure as was Tom.  “I’m going back home to Waterfield I think.  My wife says I stay here too much.”

“Don’t be in a hurry,” urged Tom.  “Can’t you stay to supper?  I’ll take you home to-night in the sky racer.  I want to talk more about the city of gold, and plan what we ought to take with us to Mexico.”

“All right,” agreed Mr. Damon.  “I’ll stay, but I suppose I shouldn’t.  But let’s mail the letter.”

It was after supper, when, the letter having been posted, that Tom, his father and Mr. Damon were discussing the city of gold.

“Will you go, even if Mr. Illingway can’t send a better map?” asked Mr. Damon.

“Sure” exclaimed Tom.  “I want to get one of the golden images if I have to hunt all over the Aztec country for it.”

“Who’s talking of golden images?” demanded a new voice, and Tom looked up quickly, to see Ned Newton, his chum, entering the room.  Ned had come in unannounced, as he frequently did.

“Hello, old stock!” cried Tom affectionately.  “Sir, there’s great news.  It’s you and me for the city of gold now!”

“Get out!  What are you talking about?”

Then Tom had to go into details, and explain to Ned all about the great quantity of gold that might be found in the underground city.

“You’ll come along, won’t you, Ned?” finished the young inventor.  “We can’t get along without you.  Mr. Damon is going, and Eradicate too, I guess.  We’ll have a great time.”

“Well, maybe I can fix it so I can go,” agreed Ned, slowly, “I’d like it, above all things.  Where did you say that golden city was?”

“Somewhere about the central part of Mexico, near the city of—­”

“Hark!” suddenly exclaimed Ned, holding up a hand to caution Tom to silence.

“What is it?” asked the young inventor in a whisper.

“Some one is coming along the hall,” replied Ned in a low voice.

They all listened intently.  There was no doubt but that some one was approaching along the corridor leading to the library where the conference was being held.

“Oh, it’s only Mrs. Baggert,” remarked Tom a moment later, relief showing in his voice.  “I know her step.”

There was a tap on the door, and the housekeeper pushed it open, for it had been left ajar.  She thrust her head in and remarked: 

“I guess you’ve forgotten, Mr. Swift, that Andy Foger is waiting for you in the next room.  He has a letter for you.”

“Andy Foger!” gasped Tom.  “Here.”

“That’s so, I forgot all about him!” exclaimed Mr. Swift jumping up.  “It slipped my mind.  I let him in a while ago, before we came in the library, and he’s probably been sitting in the parlor ever since.  I thought he wanted to see you, Tom, so I told him to wait.  And I forgot all about him.  You’d better see what he wants.”