The man on the bank shouted again. In less than two minutes the hydroplane was level with him. He knelt on one knee, lifted his rifle, and fired.

"Through the wind-screen," said Will, not turning his head. "No harm done. I'll make it fifteen."

The hydroplane swept round the first "twist" in the stream, and pa.s.sed from the sight of the look-out. Another shot rang out, and half-a-minute later two more.

"A waste of ammunition," said Will, smiling.

"Stop, senor!" cried Machado in terror, from his place in the bottom.

"We shall all be killed. His Excellency will be shot."

"Hold your tongue," growled Ruggles, "or we'll set you and his Excellency up as targets."

From some spot down-stream came the crack of another rifle, and then a second. Half-a-minute later there seemed to be an echo from a point still lower, and Azito declared that he heard two more shots even farther away.

"They're signals," said Ruggles. "Confound 'em, why are they so careful?"

"I daren't go any faster yet," said Will. "The stream's too narrow. We shall get to the tributary directly, and then I'll make her go."

A few minutes brought them to the broader stream. Then Will opened the throttle further, increasing the speed to twenty miles an hour. More shots sounded faintly in several directions. Ruggles turned his head and glanced up-stream.

"There's a canoe after us," he cried. "Indians paddling like mad, and half-a-dozen fellows with rifles."

"They can't hurt us," said Will, and laughed as he heard the rattle of an ineffective volley behind.

"It'll be a near thing, though, if they've got other canoes waiting for us down-stream. Is she going all right?"

"Perfectly. Twenty-five now, and planes beautifully. They won't hit us unless they've had practice with partridges, and if they get in the way they'll come off no better than the jaguar I ran down."

The vessel was skimming along as lightly as a bird. Ruggles gripped the side; he had no experience of this kind of navigation.

"The canoe's out of sight," he said, looking round. "We're level with the hacienda now. Two shots again. They've put a chain of lookouts all down the river."

"Thirty," replied Will, his eyes fixed on Azito, his hands firmly gripping the steering-wheel.

"A canoe putting off from the bank, senor," cried Azito. "Four men in her."

"Right bank?"

"Yes, senor."

"We'll go straight at her. Revolver ready, Ruggles?"

"For goodness' sake be careful!" gasped Ruggles. "She may capsize us."

"Thirty-five," said Will.

On flew the hydroplane.

"Are we near the canoe, Azito?" asked Will.

"She goes back, senor: better get out of the way."

"Very sensible. Duck, Ruggles: they may send a shot at us."

Next moment four bullets whizzed overhead.

"A thousand pesos if you stop!" cried the General, terrified alike by the speed of the hydroplane and the risk of being shot by his own men.

"Not for a million," said Will. "Are we near the narrows, Azito?"

"Not yet, senor."

"By Jove!" exclaimed Ruggles, "they've sent the train after us. I can see smoke through the trees."

"Forty," said Will.

He had now attained the maximum speed. He had seldom ventured to keep it up for more than a quarter of an hour at a stretch, but he was grimly determined to beat the train. No engine had yet run over the newly-laid track at a greater speed than twenty-five miles an hour: surely the driver would not risk a smash. But Captain Espejo was at the man's elbow, continually urging him to go faster. The heavy wagons rattled on behind, the men swaying this way and that, shouting, peering through the trees to the left to catch a glimpse of the hydroplane.

The sun beat down fiercely. Hot though the air was, it blew cold upon the occupants of the hydroplane as she whizzed along. Will and Ruggles were bathed in perspiration. Jose was oiling the engine.

"How are we now?" asked Will.

"I can't see for the trees. Aren't we near the narrows?"

He was answered by a volley from the bank. He ducked instinctively.

Will did not budge; his whole mind was given to the hydroplane. Would the engine stand the strain? He heard bullets slap into the wind-screen, and trembled lest one should strike the engine or find its way into the petrol tank.

"The train's almost level with us," said Ruggles. "Not more than a hundred yards behind."

At this point the railway track emerged upon the river, coming to within a quarter of a mile of it. Here the bank was clear of trees.

"How many trucks?" asked Will.

"Three, full of men. They're levelling rifles at us."

"Won't there be a smash when they come to the curve!"

"We're gaining a little, but they'll make up on us when we come to the bend."

"We must go faster. I can't leave the wheel. Ruggles, go to the exhaust valve and double the pressure."

"Good heavens! It won't stand it."

"It must! Hurry up, man."

Ruggles, as an expert mechanician, knew the risk involved. By adjusting the valve admitting pressure from the exhaust to the petrol tank it could show double the pressure on the tank gauge. By this means the explosive mixture would be enriched and more power gained. But there would be an immense risk of over-heating the cylinders.

"I don't think----" he began.