“Dancing dairy farms of Delaware!” gasped Dick. “What on earth is a sea-cow?”

“Gives salt-water milk, I guess,” grinned Tom, greatly relieved, however, to find that the blood-curdling noise was of animal and not human origin.

“That shows that you young chaps have a heap to learn,” chuckled Captain Sprowl. “The sea-cow don’t look no more like a cow than I do.”

“Ach, no! Der zee-cow iss der manatee,” put in the professor.

“That’s right, professor, and I guess we ain’t the first that’s been scared by their unholy howlings,” said the captain.

“Idt pelongs py der family Manitid?,” went on the professor, “undt is vun of der Herbiverous Cetacea.”

“In plain United States, it’s a sort of grass-eating fish,” explained the captain, “although it looks something like a big, clumsy seal. There must be a river some place about here, for they always live near the mouth of streams. I’ve seen ’em twenty feet long; but, in general, they run about twelve feet. Had one upset a canoe under me in Florida once; but there ain’t many left there now.”

“A river!” exclaimed Jack. “Well, then, that unearthly racket means that we’ve found a place to land on, for a river will do just as well as dry land so far as we are concerned.”

“By the holy poker! You’re right, lad,” declared the captain; “bear off a few points to the north there. That’s where that sea-going dairy ranch is located, to judge by the racket.”

Jack swung the air craft, as she now was, in the direction indicated. They flew above the densely growing tree tops for a short distance, and then they suddenly found themselves above the estuary of a fair-sized river. Sand-bars and small, marshy islands lay in every direction in the delta, and as the shadow of the Wondership fell upon the land below, numerous large, dark-colored animals, looking like gigantic slugs, slipped off into the water with alarmed grunts and cries.

“There’s your sea-cows,” said the captain, waving an explanatory hand downward toward the vanishing forms.

Jack swung the Wondership in a long semi-circle, and then began to glide earthwards. The descending planes were set and the ship shot downward with great rapidity. They all clung on tightly, and in a few minutes, with a mighty splash, the Wondership was resting on the surface of the river, hemmed in by the dark tangle of jungle that grew down to the water’s edge on both sides. They could see the river winding its way seaward for some distance till a bend hid its further course.

On the bar outside the surf thundered and roared unceasingly. But on the shadowy river all was silent as a country graveyard. A moist, steamy atmosphere enveloped them, strongly impregnated with the smell of rank vegetation and rotting timber.

The sun was getting low, and in the shadow of the great trees it was already twilight.

As the Wondership alighted, Jack was compelled to start the propeller once more, for the current ran so swiftly that otherwise the craft would have been borne down stream upon one of the sandy islets from which the sea-cows had vanished.

The whirr of the great screw sounded oddly amidst the solemn hush of the evening, and the Wondership began to forge ahead. It glided slowly up stream against the muddy-colored torrent that was sweeping down. The travelers’ eyes were busy in the meantime, taking in every detail of the strange scene into which they had, literally, dropped.

All at once the craft rose as though lifted from beneath and lurched so that Tom, who was standing up, was almost thrown out.

“Goodness! What’s that, an earthquake?” he gasped, gripping one of the stanchions that supported the gas-bag part of the craft.

“No, only one of those sea-cows that wished to pay his respects,” laughed Jack, as a blunt nose appeared for an instant above the turgid waters and gave a mighty grunt.

“I hope the others will be less strenuous in their attentions,” declared Mr. Chadwick. “I think that fellow must have dented his nose.”

“I don’t care about his nose so long as he hasn’t damaged us,” declared Tom. “I’m going to shoot one of those fellows if I get a chance.”

“Are they good to eat?” Jack inquired of Captain Sprowl.

“Yes, the natives like ‘em,” was the reply. “I’ve eaten Maneater steaks myself, but they’re as tough as all Billy-get-up; however, as a novelty I suppose they’re all right, as the fellow said when they asked him to eat a dish of French snails.”