The three gentlemen gave an exclamation of surprise.
"How on earth did you do that?" Mr. Hardinge exclaimed. "It would take me ten minutes to work it out on paper."
"I accustomed myself to calculate while I was in the dark, or working," Jack said quietly.
"Why, you would rival Bidder himself," Mr. Hardinge said; "and how far have you worked up in figures?"
"I did the differential calculus, sir, and then Mr. Merton said that I had better stick to the mechanical application of mathematics instead of going on any farther; that was two years ago."
The surprise of the three gentlemen at this simple avowal from a young pitman was unbounded.
Then Mr. Hardinge said:
"We must talk of this again later on. Now let us go down the pit; this young man will do excellently well for a guide. But I am afraid, Mr. Brook, that I shall have to trouble you a good deal. As far as I can see from the plan the mine is very badly laid out, and the ventilation altogether defective. What is your opinion?" he asked, turning abruptly to Jack, and wishing to see whether his practical knowledge at all corresponded with his theoretical acquirements.
"I would rather not say, sir," Jack said. "It is not for me to express an opinion as to Mr. Thompson's plan."
"Let us have your ideas," Mr. Brook said. "Just tell us frankly what you would do if you were manager of the Vaughan?"