Two hours later, just before the break of day, British bugles sounded, and the camp on the Braid Hills was immediately astir. That the enemy were about to test the efficiency of a new gigantic engine of war was unknown except to the officers and the brave man who had risked his life in order to obtain the secret of the foeman's plans.
To him the British General was trusting, and as with knit brows and anxious face the grey-haired officer stood at the door of his tent gazing across the burn to Blackford Hill, he was wondering whether he had yet obtained his coign of vantage. From the case slung round his shoulder he drew his field glasses and turned them upon a clump of trees near the top of the hill, straining his eyes to discover any movement.
On the crest of the hill two Volunteer artillery batteries were actively preparing for the coming fray, but as yet it was too dark to discern anything among the distant clump of trees; so, replacing his glasses, the commanding officer re-entered his tent and bent for a long time over the Ordnance Map under the glimmering, uncertain light of a guttering candle.
Meanwhile the Russians were busily completing their arrangements for striking an appalling blow.
Concealed by a line of trees and a number of farm buildings, the little section of the enemy had worked indefatigably for the past two hours, and now in the grey dawn the contents of the mysterious boxes, a long dark monster, lay upon the grass, moving restlessly, trying to free itself from its trammels.
It was a huge and curiously-shaped air-ship, and was to be used for dropping great charges of mélinite and steel bombs filled with picric acid into the handsome historic city of Edinburgh! Some of the shells were filled with sulphurous acid, carbon dioxide, and other deadly compounds, the intent being to cause suffocation over wide areas by the volatilisation of liquid gases!
This controllable electric balloon, a perfection of M. Gaston Tissandier's invention a few years before, was, as it lay upon the grass, nearly inflated and ready to ascend, elongated in form, and filled with hydrogen.
It was about 140 feet long, 63 feet in diameter through the middle, and the envelope was of fine cloth coated with an impermeable varnish. On either side were horizontal shafts of flexible walnut laths, fastened with silk belts along the centre, and over the balloon a netting of ribbons was placed, and to this the car was connected. On each of the four sides was a screw propeller 12 feet in diameter, driven by bichromate of potassium batteries and a dynamo-electric motor. The propellers were so arranged that the balloon could keep head to a hurricane, and when proceeding with the wind would deviate immediately from its course by the mere pulling of a lever by the aëronaut.