"Impossible," replied Mr. Roumann. "We have made some calculations, and have ascertained that this is Donati's comet—the one of 1858—and the head of it is two hundred and fifty thousand miles in diameter. The tail is many millions of miles long, and as many thick. To pass entirely beyond it would consume much time. In fact, we could not move quickly enough to escape it, as we are now being attracted out of our course toward the comet."
"How far off is it now?" asked Mark.
"About seven hundred and twenty thousand miles."
"Then we'll be up to it in about two hours," went on Mark, making a rapid calculation.
"I only hope we don't get into it, as well as up to it," commented Jack.
"We all do," observed Mr. Henderson. "But now, boys, we are going to do our best to escape. Mr. Roumann will remain in the pilot house to steer the projectile, while you and I will attend to the Etherium, motor."
"Try and see if you can get any more speed out of it," advised the German. "Use the accelerator plates, as I instructed you. Perhaps we can pass so quickly through the gaseous tail, or a portion of it, that we shall not be harmed."
"Even if it blazes?" asked Jack.
"Even if it blazes. The gas between the two shells of our projectile will absorb an enormous quantity of heat. It is our only hope."
Their hearts filled with apprehension, the two boys accompanied Professor Henderson back to the engine–room. There the scientist changed the plates on the motor, and made some adjustments, as suggested by Mr. Roumann, so that more speed would develop. Anxiously they watched the gages, to see if the motor did work any faster.