In fact, Tom and his chum were the last to arrive, which under the circumstances was not to be wondered at.

“All on deck, I reckon,” called out Jack, after he had taken a survey about him.  “There’s the signal from the flagship, Tom.  We’ve got to keep the red lantern ahead of us and fall into line.  There go the bombers to the center, and our place you said was on the left, tailing the whole bunch.”

Like a well disciplined aerial navy they fell into place, each taking its position as previously arranged.  When the formation was made complete another signal was given.  This meant the advance was now to begin, and the crossing of the German lines undertaken.

Unless there chanced to be some mistake made concerning the proper altitude required, so as to clear all possible bombardment when over the Hun lines, this might be accomplished without danger.  So far as was known, they had gauged the utmost capacity for reaching them possessed by the German anti-aircraft guns, and Jack promised himself to jeer at the futile efforts of these gunners to explode their shrapnel shells close to the speeding armada.

Something must have been underrated, however; and, in fact, few plans can be regarded as absolutely perfect.  The advancing raiders were passing over the enemy front when a furious bombardment suddenly burst forth below.

Jack could see the spiteful flashes of the numerous guns, and while the sound of the discharges came but faintly to his ears, to his consternation, all around them, as well as above and below, came sharp crackling noises, accompanied by bursts of dazzling light.

They were actually in the midst of a storm of bursting projectiles and in immediate peril of having some damage done to their swift-flying planes such as would spell ruin to the enterprise, perhaps bring instant death to some of the fliers!

CHAPTER VI

STRIKING A BLOW FOR LIBERTY

“Climb, Tom!  Climb in a hurry!”

Jack Parmly shrilled these words close to the ear of his chum.  Really, there was no need of his saying a single word, since the pilot had sensed their immediate danger just as quickly as had Jack himself.  Already Tom was pulling the lever that would point the nose of their aerial craft upward toward the stars, and take them to a much loftier elevation.

The experience was very exciting while it lasted, Jack thought.  He saw the numerous planes, forming the raiding squadron break formation in great haste, each pilot being eager to dodge the bursting shells and seek an elevation where they could not reach his flimsy craft.

It would take only one accidental shrapnel shell to cause the destruction of the best machine among them, and thus reduce the number of available airmen serving the cause of liberty.

For a brief interval the explosions continued to sound all around them.  But presently Jack was enabled to breathe easily again.  They had climbed beyond the range of the German guns, no matter how heavily charged; and, besides this, they sped along rapidly, so that the Hun lines were soon left behind.