When an attack or an artillery bombardment is on and you go to as high ground as possible for a bird’s-eye view of battle, all that you see is the explosion of the shells; never anything of the guns which are firing.  In the distance over the German lines and in the foreground over the British lines is a balloon, shaped like a caterpillar with folded wings—­a chrysalis of a caterpillar.

Tugging at its moorings, it turns this way and that with the breeze.  The speck directly beneath it through the glasses becomes an ordinary balloon basket and other specks attached to a guy rope play the part of the tail of a kite, helping to steady the type of balloon which has taken the place of the old spherical type for observation.  Anyone who has been up in a captive spherical balloon knows how difficult it is to keep his glasses focussed on any object, because of the jerking and pitching and trembling due to the envelope’s response to air-movements.  The new type partly overcomes this drawback.  To shrapnel their thin envelope is as vulnerable as a paper drum-head to a knife; but I have seen them remain up defiantly when shells were bursting within three or four hundred yards, which their commanders seemed to understand was the limit of the German battery’s reach.

Again, I have seen a shrapnel burst alongside within range; and five minutes later the balloon was down and out of sight.  No balloon observer hopes to see the enemy’s guns.  He is watching for shell-bursts, in order to inform the guns of his side whether they are on the target or not.

Riding along the roads at the front one may know that there is a battery a stone’s throw away only when a blast from a hidden gun-muzzle warns him of its presence.  It is wonderful to me that the artillery general who took me gun-seeing knew where his own guns were, let alone the enemy’s.  I imagine that he could return to a field and locate a four-leafed clover that he had seen on a previous stroll.  His dogs of war had become foxes of war, burrowing in places which wise old father foxes knew were safest from detection.  Hereafter, I shall not be surprised to see a muzzle poking its head out of an oven, or from under grandfather’s chair or a farm wagon, or up a tree, or in a garret.  Think of the last place in the world for emplacing a gun and one may be there; think of the most likely place and one may be there.  You might be walking across the fields and minded to go through a hedge, and bump into a black ring of steel with a gun’s crew grinning behind it.  They would grin because you had given proof of how well their gun was concealed.  But they wouldn’t grin as much as they would if they saw the enemy plunking shells into another hedge two hundred yards distant, where the German aeroplane observer thought he had seen a battery and had not.

“I’ll show you a big one, first!” said the general.