The wind had to be ascertained, for if a breeze was blowing across the rockets' path then they had a perverse habit of turning into the wind. That, Gilliland had explained, was because the wind put more pressure on the long stick than on the cylinder head, and so the tubes had to be aimed down-wind for an upwind target. Another calculation was the stick length, a longer stick giving more height and a longer flight, and at six hundred yards Sharpe knew the artillerymen would be sawing off a length of each rocket's tail. A third imponderable was the angle of launch. A rocket travelled relatively slowly as it left the firing tube and so the head fell towards the ground in the first few feet of flight and the angle of launch had to be increased to compensate. Modern science at war.

'Hold your hat, sir.

The smoke and flames were easily visible beneath the firing tubes, even at six hundred yards, and then, with appalling suddenness, the missiles leaped into the air. These were eighteen-pounder rockets, a dozen of them, and they sliced the air above the lingering smoke trails of the first volley, climbing, climbing, and Sharpe saw one slam off to the left, hopelessly off course, while the others seemed to have coalesced into a living flame-shot cloud that grew silently over the valley.

'Oh, God. Harper was holding the crucifix. The rockets, strangely, seemed not to be moving. The cloud grew, the flame surrounded dots were still and hovering, and Sharpe knew it'was an illusion caused by the trajectory bringing the missiles in a curve pointing straight at the two of them. Then a single dot dropped from the cloud, fire at its edges, smoke dark against the clear sky behind. The noise burst on them; a screaming roar, flame-born, and the dot grew larger. 'Down!