In order to verify Pitts’s statement, in order to swell his proposed profits to the utmost, Mitchell knew he ought to learn the “overhead” in English mills; that is, the fixed charges which, added to shop costs and prices of material, are set aside to cover office expenses, cost of operation, and contingencies.  Without this information he would have to go it blind, after a fashion, and thereby risk penalizing himself; with it he could estimate very closely the amounts of the other bids and insure a safe margin for Comer & Mathison.  In addition to this precaution he wished to have his own figures checked up, for even under normal conditions, if one makes a numerical error in work of this sort, he is more than apt to repeat it time and again, and Mitchell knew himself to be deadly tired—­almost on the verge of collapse.  He was inclined to doze off whenever he sat down; the raucous noises of the city no longer jarred or startled him, and his surroundings were becoming unreal, grotesque, as if seen through the spell of absinthe.  Yes, it was necessary to check off his figures.

But who could he get to do the work?  He could not go to Threadneedle Street.  He thought of the Carnegie representative and telephoned him, explaining the situation and his crying need, only to be told that no one in that office was capable of assisting him.  He was referred, however, to an English engineer who, it was barely possible, could handle the job.  In closing, the Carnegie man voiced a vague warning: 

“His name is Dell, and he used to be with one of the Edinburgh concerns, so don’t let him know your inside figures.  He might spring a leak.”

A half-hour later Mitchell, his arms full of blue-prints, was in Mr. Dell’s office.  But the English engineer hesitated; he was very busy; he had numerous obligations.  Mitchell gazed over the threadbare rooms and hastily estimated how much of the nine hundred and twenty dollars would be left after he had paid his hotel bill.  What there was to do must be done before the next morning’s sun arose.

“This job is worth ten sovereigns to me if it is finished tonight,” he declared, briskly.

Mr. Dell hesitated, stumbled, and fell.  “Very well.  We’ll begin at once,” said he.

He unrolled the blue-prints, from a drawer he produced a sliding-rule.  He slid this rule up; he slid it down; he gazed through his glasses at space; he made microscopic Spencerian figures in neat rows and columns.  He seemed to pluck his results from the air with necromantic cunning, and what had taken the young man at his elbow days and nights of cruel effort to accomplish—­what had put haggard lines about his mouth and eyes—­the engineer accomplished in a few hours by means of that sliding-rule.  Meanwhile, with one weary effort of will, his visitor summoned his powers and cross-examined him adroitly.  Here was the very man to supply the one missing link in the perfect chain; but Mr. Dell would not talk.