The eccentric man shook his head.

"I haven't had a good chance," he said, "but I think I'll tell her
to-morrow, and promise her one of the gold images. Then she won't
mind."

Tom was just a little bit nervous when he got ready for a trial
flight in the new dirigible balloon. To tell the truth he much
preferred aeroplanes to balloons, but he realized that in a country
where the jungle growth prevailed, and where there might be no level
places to get a "take off," or a starting place for an aeroplane,
the balloon was more feasible.

But he need have had no fears, for the balloon worked perfectly. In
the bag Tom used a new gas, much more powerful even than hydrogen,
and which he could make from chemicals that could easily be carried
on their trip.

The air craft was small but powerful, and could easily carry Tom,
Ned and Mr. Damon, together with a quantity of food and other
supplies. They intended to use it by starting from the place where
they would leave the most of their baggage, after getting as near to
the city of gold as they could by foot trails. Tom hoped to
establish a camp in the interior of Mexico, and make trips off in
different directions to search for the ruined temple. If
unsuccessful they could sail back each night, and if he should
discover the entrance to the buried city there was food enough in
the car of the balloon to enable them to stay away from camp for a
week or more.