As Bart had predicted, their squad was lined up the next day for a practical test in gas defense. They had already had preliminary drills in adjusting the masks, which had to be slipped on in six seconds. It took a long time before this stage of excellence could be reached, for some of the men were doubly slow, slow in thought and slow in action. The quicker ones had soon acquired the habit of adjusting the masks in the required time, and Frank and Bart could do it sometimes in five seconds. But the drill went on unceasingly until all acted as one man, for a single second's delay in fending off the infernal attack might mean all the difference between life and death--and such a death! It was not a pretty sight, for the masks were hideous and the men looked like weird monsters from another planet. "If only our friends could see us now!" murmured Bart to Frank in an undertone. "They'd drop dead from fright," returned the latter. "Deep sea divers have nothing on us," chimed in a third lad. "You're insulting the divers," said Billy. "If they went down looking like this, the sharks would throw a fit." At last the drill worked with clock-work precision, and the perspiring lieutenant wiped his brow and gave vent to a sigh of relief as he looked along the grotesque ranks. "I guess they're ready now," he said, turning to the sergeant. "Take them down half a dozen at a time and let them get a sniff of the gas." "_Let_ them," murmured a lad. "What a blessed privilege. Anyone would think that he was giving us a furlough for good conduct." "Save your breath and come along," admonished Billy. "You'll need all you've got in a little while." The squad was marched off to a little hut that stood in a distant corner of the camp. It was a crude creation with a door and only one window. Long before they got to it the boys could detect a faint acrid odor in the atmosphere. "Now," said the sergeant halting his men at a little distance, "you fellows break ranks and come along in single file." The single room of the hut had been filled with the same kind of gas that the Germans were using along the western front, but in greatly diluted form. "Take off your masks," commanded the sergeant, "and go along past that window one by one. Make quick time too. I want you to learn just what the gas smells like, so that you can detect it the minute it comes near you after you get to the trenches." The men obeyed orders, and, as they passed, each got a whiff of the gas that was escaping through a slight opening of the window. There was a gasp, a cough, a wry face and a hurried scuttling by as each man went through the ordeal. It is needless to say that there was no disposition to linger. Even the slowest man of the squad displayed unsuspected capacity for speed. "Look at Fatty Bates," chuckled Billy, alluding to the most ponderous member of the company. "Talk about winged heels! Mercury has nothing on him."