I have never repeated in detail the mass of calculations which Bill Todhunter made on the suggestion thus given to him. If I had, I would not repeat them here, for a reason which has been suggested already. He became fascinated with the problem presented to him. Stated in the language of the craft, it was this:

Given a moving body, with a velocity eight thousand eight hundred feet in a minute, what should be its elevation that it may fall eleven hundred feet in the transit of five-eighths of a mile?” He had not only to work up the parabola, comparatively simple, but he had to allow for the resistance of the air, on the supposition of a calm, according to the really admirable formulas of Robins and Coulomb, which were the best he had access to. Joslyn brought me, one day, a letter from Bill Todhunter, which shows how carefully he went into this intricate inquiry.

Unfortunately for them all, it took possession of this spirited and accomplished young man. You see, he not only had the mathematical ability for the calculation of the fatal curve, but, as had been ordered without any effort of his, he was in precisely the situation of the whole world for trying in practice his own great experiment. At each of the two X X of Joslyn’s map, the company had, as it happened, switches for repair-trains or wood-trains. Had it not, Bill Todhunter had ample power to make them.

For the “experiment,” all that was necessary was, that under the pretext of re-adjusting these switches, he should lay out that at the upper X so that it should run, on the exact grade which he required, to the western edge of the ravine, in a line which should be the direct continuation of the long, straight run with which the little map begins.

An engine, then, running down that grade at the immense rapidity practicable there, would take the switch with its full speed, would fly the ravine at precisely the proper slopes, and, if the switch had been rightly aligned, would land on the similar switch at the lower X. It would come down exactly right on the track, as you sit precisely on a chair when you know exactly how high it is.

“If.” And why should it not be rightly aligned, if Bill Todhunter himself aligned it? This he was well disposed to do. He also would align the lower switch, that at the lower X, that it might receive into its willing embrace the engine on its arrival.

When the bold engineer had conceived this plan, it was he who pushed the others on to it, not they who urged him. They were at work on their daily duty, sometimes did not meet each other for a day or two. Bill Todhunter did not see them more than once in a fortnight. But whenever they did meet, the thing seemed to be taken more and more for granted. At last Joslyn observed one day, as he ran down, that there was a large working-party at the switch above Drums, and he could see Bill Todhunter, in his broad sombrero, directing them all. Joslyn was not surprised, somehow, when he came to the lower switch, to find another working-party there. The next time they all three met, Bill Todhunter told them that all was ready if they were. He said that he had left a few birches to screen the line of the upper switch, for fear some nervous bungler, driving an engine down, might be frightened, and “blow” about the switch. But he said that any night when the others were ready to make the fly, he was; that there would be a full moon the next Wednesday, and, if there was no wind, he hoped they would do it then.

“You know,” said poor Joslyn, describing it to me, “I should never have done it alone; August would never have done it alone; no, I do not think that Bill Todhunter himself would have done it alone. But our heads were full of it. We had thought of it and thought of it till we did not think of much else; and here was everything ready, and neither of us was afraid, and neither of us chose to have the others think he was afraid. I did say, what was the truth, that I had never meant to try it with a train. I had only thought that we should apply to the supe, and that he would get up a little excursion party of gentlemen,—editors, you know, and stockholders,—who would like to do it together, and that I should have the pleasure and honor of taking them over. But Todhunter poohed at that. He said all the calculations were made for the inertia of a full train, that that was what the switch was graded for, and that everything would have to be altered if any part of the plan were altered. Besides, he said the superintendent would never agree, that he would insist on consulting the board and the chief engineer, and that they would fiddle over it till Christmas.

“‘No,’ said Bill, ‘next Wednesday, or never! If you will not do it then, I will put the tracks back again.’ August Todhunter said nothing; but I knew he would do what we agreed to, and he did.

“So at last I said I would jump it on Wednesday night, if the night was fine. But I had just as lief own to you that I hoped it would not be fine. Todhunter—Bill Todhunter, I mean—was to leave the switch open after the freight had passed, and to drive up to the Widow Jones’s Cross Road. There he would have a lantern, and I would stop and take him up. He had a right to stop us, as chief of repairs. Then we should have seven miles down-grade to get up our speed, and then—we should see!