Having studied my map I saw that my most direct route would be over Tonbridge, thence by the railway line to Sevenoaks, and then north-east till I could pick up Gravesend—which would be easy on account of the river Thames—and afterwards due north would bring me to G, which would be easily distinguishable by certain landmarks.
We had wheeled out the machine, and I was tuning her up before starting, both Teddy and I ready in our air-clothes, when Theed, who was giving the machine a final look round, suddenly gave vent to an ejaculation of dismay.
'Why look, sir!' he cried. 'What's this?'
I hopped quickly out of the pilot's seat and, joining him, saw to my surprise that, beneath the wooden petrol-tank a fine insulated twin-wire had been placed, and upon it, tacked lightly to the wood, was a small disc of some black-looking material through which the fine wire ran.
In breathless eagerness I traced the wire and, to my horror, saw what a devilish contrivance it was. The twin-wire had been connected up to the battery that ran the lamp over my map and instruments, therefore had I switched on the light at night, it would have failed, for it was intended that the current should ignite that little disc of inflammable material and explode my petrol tank behind me!
Truly, the device of those crafty and subtle enemies was a devilish one. That wire had been connected up by an Invisible Hand—by the hand of one who certainly knew the most vulnerable point of the machine.
