Before they obtained a full view of Keshan itself they perceived evidences of a considerable concentration of troops. At several points around the town there were extensive encampments. Clouds of dust to the north, east, and north-east betrayed the movements of troops or convoys. And when they were still about two miles from the town they heard the familiar rattle of machine-guns and the long crackle of rifle fire. But they were too high up to feel any anxiety, and while Burton wheeled round and round in an extensive circle, Hunter busily plotted out on his map the positions of the camps, and made notes of the directions of the movements, the estimated number of the battalions, and the nature of their arms. After a while Burton began gradually to drop, in order to give Hunter a chance of recognising gun emplacements. At about two thousand feet the enemy opened fire. White and creamy puffs of shrapnel floated and spread in the air. A shell burst some distance beneath them, another above them, and soon the machine was cleaving its way through a thin cloud of pungent smoke. It appeared that at least six guns were at work. "Better get out of this," shouted Hunter. "I’ve got about enough information." "We’ll go a little farther north," replied Burton, "to see if any reinforcements are coming up towards Keshan." "All right, but go a bit higher; I heard two or three smacks on the planes just now." Rising a little higher, Burton swept round to the north. In a minute or two Hunter was able to see that the hill track from Rodosto was choked with transport of all kinds. Right and left, every possible route from Constantinople and Adrianople was equally congested. It was clear that a vast army was being concentrated within striking distance of Gallipoli, and on the flank of any force moving eastward from Enos or any other point of disembarkation. Burton then headed west towards the Maritza, intending to return by way of Enos and discover, if possible, what force the Turks had available for the defence of that place. They were passing somewhat to the north of Keshan, to keep out of the way of the batteries, when Hunter suddenly caught sight of an object like a large bird low down in the sky on their left hand. A few moments’ scrutiny through his glasses confirmed the suspicions which had seized him on the instant. "An aviatik, coming our way," he called. "Won’t catch us," responded Burton with a smile. "Stay and fight it?" "It’s tempting, but we mustn’t. It won’t do to run risks when our job’s to collect information." Hunter acquiesced with a sigh. Burton shifted his course a point or two to the west, so as to run nearly parallel with the enemy’s aeroplane. A moment or two later he gave a start of alarm. "What’s the matter?" asked Hunter. "Afraid there’s a leak. The petrol gauge is falling faster than it ought. They must have knocked a hole in the tank. See if you can find it."