"Perhaps you have a better idea," Mayer pouted.
"Perhaps I have," the lieutenant rejoined. "We must use some sort of signal to be repeated at regular intervals."
"Surely you can't mean flashes of light or anything like that," Mayer said.
"Certainly not. Anything visible would betray our presence to the Martians. What I have in mind is a sound of some sort—something which might be heard here under normal conditions—something loud enough and distinctive enough to be recognized at a distance."
Sullivan knitted his brows for a moment or two and then exclaimed: "I have it! A jackant!"
"And what in cosmos is a jackant?" Mayer wanted to know.
"If you want that question answered, put on your thermal suit and come outside with me."
Sullivan was already attired in the electrically heated costume which earth-folk usually wore for protection against the bitter, nocturnal frigidity of the planet Mars. Responding to Sullivan's suggestion, Mayer put on his thermal suit and followed the lieutenant into the airlock.
"Is it really necessary to use the airlock?" he asked Sullivan.
"Not necessary but advisable," the older man told him. "Making our exit this way will enable us to conserve both the warmth and the pressure of the air inside the spaceship."
When the outer port was opened, Mayer felt a sudden chill which, in spite of his heated garment, made his teeth chatter. He also discovered that the atmosphere was distressingly rarefied. In order to supply his oxygen-hungry lungs with sufficient air he had to breathe furiously, like a runner at the end of a ten kilometer race.
"Listen," he heard his companion pant.
Mayer listened. For a while he could distinguish only the sound of his own breath as it hissed in and out of his distended nostrils. Then, from a remote portion of the desert a startling cry was wafted to him. It was a weird, eerie conglomeration of chirping, howling and braying.
"What in the galaxy is that?" he asked in a labored whisper.
"A jackant," Sullivan told him.
"A what?"
"A jackant, you gink. Surely you must know what a jackant is. There's a pair of them in the International Zoological Gardens at Rome."
"Never been there," Mayer admitted. "Is it a bird, or beast or a bug?"
"Don't ask me—I'm no authority on Martian zoology. The Jackant has six legs like a bug and feathers like a bird but it suckles its young like a mammal—so take your choice."
"How big is it?"
"About the size of an Airdale dog. There goes another one—hear it?"
"Of course I hear it. Do you think I'm deaf?"
Ignoring this impertinent question, Sullivan said: "They tell me you are pretty good at impersonations. Let's hear you imitate a jackant."
Obligingly Mayer threw back his head and uttered a cry: "Chir-r-r-ak—ow-w—w-yaw-gee-yaw!"
It was so loud and penetrating that Captain Brink heard it through the insulated shell of the Cosmicraft. His face appeared at the observation port which was closest to the airlock. The expression of surprise on his countenance made Sullivan chuckle.
"Cosmilossal!" he exclaimed, giving Mayer a slap on the back which
