And then the lightning struck, suddenly and hard. Once each week an outsider from the engineering department of some big industrial plant, or large university, lectured to the entire student body of the Marshallton Tech in the assembly-room, and there were some of these talkers who got much pleasure out of it. Not only was it interesting to hold forth to a lot of eager, responsive boys on subjects that elicited their curiosity, as the building of great dams and bridges, the tunneling under mountains, the erection of mighty machines, but it was also diverting to hear their various comments which also led to a comparative estimate of their understanding.
Davidson, chief mechanical engineer of a great mill building corporation, was especially interested in the personal equation concerning the students, particularly after Bill Brown bad asked him a lot of questions, some of which he had replied to rather lamely. Even more as a matter of getting back at this young investigator who sat with a crutch held before him and regarded these replies with a smile than for the desire to measure minds, Davidson gathered a few catch problems that were stumpers, and upon his third visit, after talking awhile he switched off on the subject of problems, short cuts to solutions and then put a question, looking hard at Bill, as though uttering a challenge.
“Now, how would you go about it,” he shot at his audience, “if you were asked to measure the cubic contents of an electric light bulb?”
A number of smiles greeted the question; these may have been from lads mostly in the advanced courses who knew the trick. The lecturer asked for hands to be raised by those who thought they could do it, and noting with satisfaction that the crippled boy was not among the number who responded, he began hearing them, one at a time.
“Measure it outside and allow for the thickness of the glass,” said one fellow.
“But how about the carbon inside?” asked Davidson.
“Break the glass and measure the loop,” called out a soph.
“How many of you would go at it in that way?”
A number of hands went up, some rather reluctantly, as though their owners scented a trick.
Davidson still eyed the cripple. “How would you do it?” he asked.