of ma diaphragm ev'ry time I circumnavigates erbout in disher flyin' ship makes me wanter express mahself in de mos' scatterin' kin' ob er way—I hopes you gits ma meanin' clear?"
Jack was laughing so that he could not speak, but Mark managed to say:
"You mean that the motion of the aeroplane gives you a feeling of mal de mer?"
"Dat's wot I done said," Wash replied, seriously. "I nebber in ma life felt so mal-der-merry as I do at dis present onauspicious 'casion; an' if dat mal don't stop merryin' purty quick, I suah shall be—ugh!—sick ter ma stummick!"
This wail fairly convulsed Jack Darrow and Mark Sampson; but they knew that if Wash paid more attention to his duties and thought less about his own situation he would be better off. Mark insisted on his going at once into the tiny, covered "galley," as the boys called it, hung amidships, in which were the means of heating water, making coffee, and cooking certain simple viands in their stores.
Wash went to his duties grumblingly; but he was an ingenious and skillful cook and when he got to work he forgot his "feeling of mal-de-merry."
It was now approaching midnight and the flying machine had been steadily traveling northward for some hours. Both Andy Sudds and the professor awoke and offered to relieve the boys in their work. But Mark had taken Jack's place in the controller's seat and neither he nor his chum felt that he wished to give over the guidance of the Snowbird to anybody else.
Now, some distance ahead, the peak of Mt. Katahdin, gloriously mantled in moonlight, rose before them. Their direct course lay over the summit of this eminence, and Mark decided that it would be better to rise to a higher strata and cross the mountain than to swing around it. Therefore Mark raised the bow of the flying machine and she darted upward on a long slant, drawing ever nearer to the shining peak of the great mountain. The night air was chill—it had been cool when they left the earth—and as they rose to the rarer ether it was evident that they would find a degree of temperature far lower than the usual summer heat.
Mark kept the Snowbird scaling swiftly upward, mile after mile; but the long tangent at which he had started to clear the summit of Katahdin did not prove sufficient, and by and by they found themselves within a very few yards of the rocky side of the peak.
Out of a dark glen a spark of light suddenly shot—almost like a rocket in swiftness. Jack saw it first and cried:
"See that! What is it? What do you make of it?"
"A shootin' star, I declare!" said Andy Sudds.
"Nothing of the kind," exclaimed Jack, quickly. "A star could not shoot up from the earth."
"Wot's dat says somebody's a-shootin' at us?" gasped Washington White.
"If dey punctuates our tire, we'll suah go down wid a big ker-smash!"
The professor, however, watched the "shooting star" for some moments without speaking, and then rapidly made his way to Mark's side.
"Send your 'plane up in spirals, boy!" he commanded. "Don't let that light rise over us. Be quick, now!"
"What is it, Professor?" asked young Sampson, as he obeyed the scientist's injunction.
"I am sure it is a light in the bow of another airship—but what manner of ship she is, or who drives her, I cannot guess," declared Professor Henderson, gravely.
"Another airship!" cried Jack, who overheard him. "What do you know about that?"
Mark handled the Snowbird with great skill, and the powerful craft mounted much more swiftly than the distant spark of light. The spiral course the 'plane now followed carried it at times much farther from the mountain side than it had been when first the strange light was noticed. That light followed the Snowbird up and up in similar spirals, and the boys were soon convinced that Professor Henderson's discovery was a fact. The lamp was in the bow of another air craft.
"But why should we keep over them?" asked Jack. "There is no danger; is there?"
"We do not know who they are," said the professor, shortly. "The craft came right out of a fastness in the mountain-side—a place difficult to reach, and which would not seem to attract aviators of the ordinary class." "I know what he is thinking of," cried Mark, suddenly. "I read in the paper that the Department of Justice officers are after some big smugglers and that it is believed the criminals, in going back and forth into Canada, use some kind of an aerial craft. Isn't that so, Professor Henderson?"
"I had the fact in mind. The flying machine is being put already to uses that are not commendable, to say the least. The Maine and Canadian border has for years been used by bands of smugglers, and if one of these gangs have purchased and can use a flying craft, they may make the revenue men a deal of trouble."
"You're right, sir. And I read likewise that the government officers proposed using an aeroplane themselves to track the smugglers. Perhaps the villains, if that is their ship below us, may take us for secret service men."
As he spoke the lamp so far below them darted up at a sudden and sharp angle, there sounded the sharp crack of some weapon, and Washington White jumped and screamed.
"Gollyation!" he bawled. "Dem fellers is suah tryin' ter punctuate us!"
Through the blackness of the night a distant voice hailed the pilot of the Snowbird.
"Ahoy! ahoy! Who goes there?" was the cry, and it was repeated twice.
CHAPTER V
BETWEEN TWO PERILS
Mark Sampson, having all the mechanism of the flying machine under his immediate control, had it in his power to increase speed and seek to escape the second airship. And Jack wondered why his chum did not immediately send the Snowbird flying at increased speed over the top of Mt. Katahdin and so seek to escape the menace below.
But the young fellow at the controls of the Snowbird had an advantage over his companions that Jack had forgotten. He could hear sounds at a much greater distance than they, and much clearer.
This was because of an invention of Professor Henderson—a small instrument similar to part of the ordinary telephone. The sensitive disk was a form of radio receiver which could be attached to any aviator's helmet, and was being put into general use by pilots. The two boys always adjusted this whenever they were strapped upon the pilot's seat.
Thus, although the report of the gun had sounded but faintly to the other members of the party, to Mark it seemed as though the explosion was within a hundred yards. The voice hailing them likewise seemed to ring in his ears very plainly; and beyond the words somewhat distinguished by his companions the young operator of the Snowbird could make out a further phrase spoken by the person who hailed from the other air-craft.
"Halt in the name of the law!"
Those were the sharp words Mark had caught, and for that reason he hesitated to increase the Snowbird's speed.
In a strap hung near his left hand was a transmitter. Without taking the advice of any of his companions in the flying machine, Mark seized it, put it to his lips, and replied to the hail:
"Ahoy! what do you want?"
Instantly the voice rose from the black abyss below them:
"Heave to! Stop in the name of the law!"
That time the professor and Jack heard the words spoken by their pursuer.
"What do you know about that?" demanded Jack. "'In the name of the law', no less!"
Professor Henderson jumped to the same conclusion that Mark had, and that instantly. "It may be the Secret Service men themselves," he said. "Ah, Andrew! it is just as well to withhold your fire until we know