"You won't do any such thing," came the firm answer.  "While you are at school you two fellows need your evenings for rest and study, and your Saturdays for the school-team sports.  Only when there isn't a game on in which you are a contestant will I allow you to help John on the machine--even if it isn't finished for five years.  I have been thinking this situation over for some time, for I have seen it coming," went on the great publisher after a moment's pause; "and I have come to the conclusion that the best thing I can do to hustle our ship along is to call in another workman on the job, some chap we can trust and who knows how to handle tools.  In fact, if he were a regular airplane mechanic it would be all the better."