In the excitement of the chase the hours sped quickly—so quickly that Whittinghame uttered an exclamation of surprise when Dacres announced that the frontier was passed and that the "Meteor" was above Valderian territory.
"Are you quite sure?" he asked.
"Of course, sir, I couldn't obtain an absolutely correct reading on account of the motion and the slight refraction of the glass scuttles," replied Dacres. "But I am quite convinced that, allowing a margin of safety, we are between twenty and thirty miles over the dividing-line."
"There are the Sierras," announced Setchell, pointing to a row of snow-topped peaks. "If the 'Libertad' doesn't begin to ascend, she'll have a stiff climb."
"We have her right enough," said Whittinghame, rubbing his hands gleefully. "We have her. Before she can ascend sufficiently to clear those peaks we'll have overhauled her."
"Unless she finds a pass between the mountains," added Dr. Hambrough, who, in his shirt-sleeves, was going through the contents of an ambulance-chest.
Nearer and nearer drew the formidable chain of peaks. Both airships were continually ascending, but it was quite apparent to the crew of the "Meteor" that unless the "Libertad" rose at a fairly steep angle she would never clear the summit. Even if she attempted it her speed must be greatly retarded, during which time the "Meteor" would have overlapped her antagonist.
Suddenly the Valderian airship ported her helm, slowing down as she did so. Whittinghame instantly ordered the "Meteor's" motors to be stopped.
"She means to show fight!" he exclaimed.
Once again Durango had gained the better position by skilful manoeuvring. Owing to the great difference in height the "Meteor's" bombs stood little chance of hitting the target, immense though it was. She was provided with only two quick-firing guns that could be trained immediately beneath her; while the six weapons on vertical mountains on the "Libertad's" upper platform could be brought into play.