It would appear, however, that Durnford's mounted Basutos discovered and fired on a portion of the Umcityu regiment, which, forgetting its orders, sprang up and began to charge. Thereon, accepting the position, the other Zulu regiments joined the movement. Very rapidly, and with the most perfect order, the impi adopted the traditional Zulu ox-head formation, namely, that of a centre and two horns, the centre representing the skull of the ox. In this order they advanced towards the English camp, slowly and without sound. Up to this time there had been no particular alarm in the camp. The day was bright and lovely, with a hot sun tempered by a gentle breeze that just stirred the tops of the grasses, and many men seem to have been strolling about quite unaware of their imminent danger, although orders were given to collect the transport oxen, which were at graze outside the camp; not for the purpose of inspanning the waggons, but to prevent them from being captured by the enemy. One officer (Captain, now Colonel, Essex) reports that after the company had been sent out, he retired to his tent to write letters, till, about twelve o'clock, a sergeant came to tell him that firing was to be heard behind a hill in face of the camp. He mounted a horse and rode up the slope, to find the company firing on a line of Zulus eight hundred paces away to their front. This line was about a thousand yards long, and shaped like a horn, tapering towards the point. It advanced slowly, taking shelter with great skill behind rocks, and opened a quite ineffective fire on the soldiers. Meanwhile the two guns were shelling the Zulu centre with great effect, the shells cutting lanes through their dense ranks, which closed up over the dead in perfect discipline and silence. The attack was now general, all the impi taking part in it except a reserve regiment that sat down upon the ground taking snuff, and never came into action, and the Undi corps, which moved off to the right with the object of passing round the north side of the Isandhlwana hill. On came the Zulus in silence, and ever as they came the two horns crept further and further ahead of the black breast of their array. Hundreds of them fell beneath the fire of the breech-loaders, but they did not pause in their attack. Ammunition began to fail the soldiers, and orders having reached them--too late--to concentrate on the camp, they retired slowly to that position. Captain Essex also rode back, and assisted the quartermaster of the 24th to place boxes of ammunition in a mule cart, till presently the quartermaster was shot dead at his side. Now the horns or nippers of the foe were beginning to close on the doomed camp, and the friendly natives, who knew well what this meant, though as yet the white men had not understood their danger, began to steal away by twos and threes, and then, breaking into open rout, they rushed through the camp, seeking the waggon road to Rorke's Drift.