direction only, as a lantern does. And a powerful electric lamp, such as these appear to have been, would be visible a lot farther than an ordinary railway lantern. As a guess, after seeing the conditions in that infernal tunnel, I should think that to be seen at a distance of half a mile, the lamps must have been of at least a hundred candle-power each. And that raises an even bigger problem than how the chap got into the tunnel.â
âWell, letâs have it,â said Arnold. âOne problem more or less wonât make much difference.â
âHere you are, then. Electric lamps donât produce light of themselves. They have to be supplied with current. Where did the chap get his current from? Thereâs no electric supply main running through the tunnel, you know.â
âIâm well aware of that. The man carried a battery with him, of course. Just as we carry batteries in our torches.â
Merrion shook his head. âThe lamps in our torches arenât a hundred candle-power, or anything like it. Being quite small, they take very little current, and a small battery is enough to supply it. But to supply current for these lamps nothing lighter than a fair-sized motor-car battery would do. Have you ever tried carrying one of them about? Theyâre devilish heavy, I can tell you. It would be a terrific feat to carry one into the middle of the tunnel and out again.
âYet, by using ordinary household bulbs, this man deliberately saddled himself with the necessity for such a battery. Why did he use that kind of lamp? A couple of large-sized torches, or even one, with a movable red and green screen fitted to it, would have done just as well. By means of a lens and reflector a torch is made to give as much light as one of these lamps. But this is done by concentrating the light in one direction only. The only possible reason for using ordinary lamps, with their much greater expenditure of current, would be to obtain the advantage of the light showing all round. But, in heavenâs name, why should this chap have wanted that?â
âI havenât the least idea,â Arnold replied, shrugging his shoulders. âYour imagination is leading you away from the point. What reason the chap may have had for using lamps instead of torches canât possibly matter. Here are the lamps, or whatâs left of them. Thatâs sufficient proof to me that the chap used them, and that he had with him a source of current from which to light them up. And when heâd done with them, he chucked them aside in the tunnel. So much is plain enough.â
Merrion picked up the bits of flexible cord and examined them intently. âOur friendâs proceedings strike me as bordering on the insane,â he said. âHe burdens himself with a cumbrous battery, when a far lighter torch would have served him equally well. When he has finished with his apparatus, he throws away the lightest part, and keeps the heaviest. For he certainly didnât leave the battery in the tunnel, or we should have found it. And he doesnât just disconnect his flexible. He breaks it violently, as you can see for yourself if you look at it.â
âIâm not interested in details like that,â said Arnold impatiently. âDo look at the matter sensibly, thereâs a good chap. We know now that Prentice and Haynes werenât imagining things when they saw those lights. Therefore a man had entered the tunnel with the definite object of slowing down the train. Why should he want to slow down the train? Tell me that.â
âSo that he could board it, I suppose,â Merrion replied. âLook here, Arnold, have you ever climbed into an English railway carriage when it wasnât standing at a platform?â
âYes, I climbed into that first-class coach when it was standing in the siding at Stourford yesterday morning.â
âWould you have liked to have done so with a battery