In a few seconds there was a sudden throb of the engine which instantly developed into such a roar that to speak to Roseye at my side became quite impossible. We shot forward into the darkness, a sharp gust of wind struck our faces, we bumped for a few seconds along the ground, and then left the earth, the noise of the powerful engines almost splitting the drums of our ears. I saw before me a belt of trees and, pulling over the lever, rose above them, described a semicircle, and then, watching my compass, rose at once and headed for Stockhurst church, where I knew Teddy was anxiously awaiting our arrival. I know that Roseye, with the icy wind cutting her eyes, lowered her goggles, but after that I fear I became too occupied to notice anything further. It was a wild night-flight, and I knew that both our lives were now in jeopardy. CHAPTER EIGHTEEN. THE TRI-COLOURED RINGS. Almost as soon as we rose we saw straight before us a beam of reddish light moving swiftly northward in the direction of London. For a few seconds it was shut off, shone out again, and then went out. I knew it to be from a railway engine, the stoker of which had been firing up. Moving trains, notwithstanding the pulling down of carriage-blinds, and the darkening of railway platforms so that persons break their legs in descending, or getting out at a supposed platform and falling upon the line, form the best guides for aircraft at night. By following an express locomotive, which must be stoked at frequent intervals, and looking out for the coloured signal-lights along the line, an airman can always reach the London area. I had, when night-flying at Hendon before the war, often guided myself home by following an up-express. So terrific was the roar of my new engine that I could only communicate with Roseye by signs. I pointed at the moving train and, understanding my gesture, she nodded. As we rose higher and yet higher into the calm starlit sky, the earth beneath us became increasingly mysterious and misty. Here and there dim lights showed, single lights of scattered cottages unseen by rural constables, or improperly obscured lights from the larger houses. Soon some red and green lights showed away on our left, and I knew that in the valley there ran the main railway line to London. By day, at an altitude of 2,500 feet, the whole surface of the earth appears perfectly flat, hills and valleys seeming to be on the same level. Therein lies one of the dangers of aerial navigation. The contour of the earth is quite indistinguishable when one is half a mile high, therefore the altimeter is not of very great use--and more especially so at night. The instrument only records the number of feet above sea-level, and not above the earth. Thus, a pilot flying by night can very easily pass over a valley and suddenly find himself encountering a range of high hills with a fatal belt of trees or row of houses.