"Say!" Joe remonstrated. But just then Philip Burton, telegraph operator and genial good friend of all three of the lads, bustled into the room, a sheaf of yellow telegrams in his hand. "What's all the excitement?" he asked, striding toward the typewriter just left by Jerry. "Why," explained Slim, "Joe's just done something that means something." "Impossible," said Mr. Burton, turning toward them with one of those irresistible smiles which long ago had made him the boys' confidant. "If you don't believe it, read this," commanded Jerry, thrusting the paper before the telegrapher's eyes. Mr. Burton read it through and then turned to the three boys again. "Well?" he asked. "It means what it says," explained Jerry. "Now is the time for all good men to come to the aid of their country." "And we're 'good men,' ain't--aren't we?" demanded Slim, drawing in his stomach and throwing out his chest as he straightened up to his full five-feet-four-inches "in his gym suit." "None better anywhere," said Mr. Burton in a tone that showed he meant it. "But just how do you contemplate going to the aid of your country?" It was Joe's turn to say something, and he did. "By enlisting," he announced, briefly but firmly. "Yes," agreed Slim, "that's it, by enlisting." "Uh-huh," said Jerry, nodding his head vigorously and watching Mr. Burton's face for evidence of the effect of their decision. "And when did you determine upon that?" the telegrapher asked, with increasing interest. "Well," said Slim, his face now painfully red from his efforts to keep chest out and stomach in, "it was finally decided upon just now, although we have talked about the thing in a general way many times." "You really mean to enlist--all three of you?" Mr. Burton demanded. "Yes, sir," they chorused, "all three." "Good!" exclaimed the man who had been their friend and helper. "Fine! I'm proud of you," and he proceeded to shake hands heartily with each in turn. "Have you decided upon the branch of the service you intend to enter?" he then asked. Joe looked at Jerry, Jerry looked at Slim, and Slim cast a helpless glance back at Joe. "I see you haven't," said Mr. Burton hastily, "and I'm glad of it. Now how about the Signal Corps?" "What do men in the Signal Corps do?" asked Jerry. "Do they fight?" demanded Slim. "Yes," Mr. Burton replied, "they do some fighting on their own account, and often in tough places and against discouraging odds. But they do even more than that. Without their assistance no general would dare lay plans for a battle. The Signal Corps keeps the commanders posted, not only as to the whereabouts and disposition of his own troops, but also of those of the enemy. The Signal Corps is the telephone, the telegraph, the wireless, and often the aviation section as well, of the American army, and often of the American navy, too." "Isn't that great?" exclaimed the breathless Slim, as Mr. Burton went over to the ticker to answer the code call for his station.