It is a splendid sight to see a Royal Horse battery come into action. The teams advance at the gallop. At the signal "Halt! Section front," the gunners jump down from their seats on the gun carriages and limbers. Two of them lift the trail of the gun off the hook at the back of the limber, and two others man the wheels of the gun; the teams drive on with the limbers, the guns are spun round, and in three seconds are ready for firing. Before the gun can do its work properly, the range--that is, the distance between the gun and the target--must be found. For this purpose trial shots are fired. The gunners guess the range, and then fire at a point some hundred yards less than the supposed distance. They watch for the puff of smoke which arises when the shell strikes the ground. If they see it in front of their target, they know that the range is short. Then another shell is fired one hundred yards beyond the supposed range. If this falls behind the target, they know that the range is too long. The next shot is fired at a distance midway between the short shot and the long shot, and thus the correct range is found. In order that the puffs of smoke may be distinctly seen, observers are sent forward to the right or left of the line of fire to watch where the shells fall. Sometimes they are provided with telescopic iron ladders, which they mount in order to have a better view. Field telephones are sometimes laid so that the observers can communicate with the batteries. If an enemy has dug himself in and is firing from concealed trenches, aeroplanes are sent up to spy out the land. When the aviators discover a trench they drop down bits of tinsel, which glitter in the sunshine, or a bomb, which ignites when it strikes the ground, and sends up a cloud of smoke. The gunners then know where their target is. Sometimes the range is found by means of an instrument known as the range-finder. When firing begins the aviator watches the shots, and signals to the gunners until they are aiming correctly. The aeroplanes also discover the position of the enemy's artillery, so that it can be fired at. In order to deceive the airmen, the guns are covered with straw or boughs, so that they cannot be easily detected from above.