The doctor sat down, and all eyes were once more turned toward Dutch. Nearly every lad in the class could have given some sort of answer, for they had seen the curious glass drops broken by their regular teacher. But, as it happened, Dutch had been absent when that subject came up, and, as he made it a practice never to inquire what went on in the lecture room when he was not present, he was wholly at sea regarding the drops. He had a hazy idea regarding them, however, and resolved to hazard a recitation. It was better than complete failure.
As “every schoolboy” (to quote a well known authority) knows what the Prince Rupert drops are, I will only state that they are globules of glass, pear shaped, with a long thin “tail” of the same brittle material. They are formed by dropping molten glass into water. The outside cools quickly, a long tail is formed, and there results an unequal strain on the glass, because the outside part has cooled faster than the inside. The instant a small part of the “tail” is broken off, the entire drop crumbles to glass-dust, the pressure once more being equalized.
It was this object and phenomenon that Dutch was called on to recite about. He rose in his seat, and began with an air of confidence that he did not feel:
“The Rupert drops illustrate the power of hot water or steam. They are globules of glass, filled with water, and, when they are heated, they burst to pieces, showing the expansive force of heat.”
The class wanted to roar. Dr. Churchill raised his eyebrows in surprise. Dutch had described another glass object used in the class room, and his explanation of that had been correct, but it was as different from a Prince Rupert drop as a ham sandwich is from chicken.
“Ah—um,” mused the president, putting on his glasses, and gazing at Dutch through them. “Very interesting, Mr. Housenlager—very—but—hardly what I asked you.”
“I—er I—er—I’m afraid I’m not prepared, sir,” stammered the fun-loving youth, and the smiles went round the class.
“Too bad—don’t you want to try again?” asked the president.
Dutch thought, and thought hard, but the more he tried to use his brain, the more foreign Prince Rupert seemed to him. He gave it up.
“Failure,” murmured Dr. Churchill, as he marked it down against Dutch. “You may try, Parsons.”