'Yes; but I'm afraid it's the last one we shall ever get like it,' replied the major.

Biggles looked up with a puzzled expression. 'How's that?' he asked quickly.

'The Huns are using that camera now.'

'Camera! Why, is there only one of them?'

'There is only one camera in the world that can take a photograph as perfect as that, and the Germans produced it. It's all in the lens, of course, and I've an idea that that particular lens was never originally intended for a camera.

It may have been specially ground for a telescope, or microscope, but that is really neither here or there. As far as we are concerned, the Germans adapted it for a camera, and we soon knew about it by the quality of the photographs that fell into our hands from German machines that came down over our side of the Lines.

I will give you the facts, although I must be brief, as I have much to do. About three months ago we had a stroke of luck - a stroke that we never expected. The machine that was carrying the camera force-landed over our side, although force-landed is hardly the word. Apparently it came down rather low to avoid cloud interference, and the pilot was killed outright by archie, in the air. The observer was wounded, but he managed to get the machine down after a fashion.

As soon as he was on the ground he fainted, which may account for the fact that he did not destroy or conceal the camera before he was taken prisoner. That was how the camera fell into our hands, and we lost no time in putting it to work. Needless to say, we took every possible precaution to prevent the Germans getting it back again.

'We had it fitted to a special D.H.4,* the pilot of which had orders on no account to cross the Lines below eighteen thousand feet. Naturally, we had to send the machine over the Lines, otherwise the instrument would have been no use to us; we didn't want photographs of our own positions.

'This pilot also had instructions to avoid combat at all costs, but if he did get into trouble, he was to throw the camera overboard, or do anything he liked * de Havilland 4 British two-seater day bomber 1917-1920. W. E. Johns piloted the D.

H.4 with 55 Squadron in 1918.

with it as long as the Germans didn't get hold of it again.'

'What was to prevent the Huns making another camera like it? Couldn't they make another lens?' asked Biggles.

'Good gracious, no! A lens of that sort takes years and years of grinding to make it perfect. I doubt if that particular one was produced inside five years, and being worked on all the time.

I see.'

'Well, you will be sorry to hear that the camera is now in German hands again.'

'How the d.i.c.kens did they get it?' exclaimed Biggles.

The major made a wry face and shrugged his shoulders.

'We may learn after the war is over,' he said. 'Perhaps we shall never know The two officers who were in the D.H.4 are both prisoners, so we have no means of finding out.

One can only imagine that they were shot down, or were forced down by structural failure, although how and why they failed to destroy the camera, knowing its vital importance, is a mystery.

'We were sorry when the machine failed to return - and we were astounded when the Germans began using the camera again, because we felt certain that our fellows would have disposed of it, somehow or other. Naturally, if the machine had been shot down from a great height, or in flames, the camera would have been ruined. Well, there it is.

Our agents in Germany have confirmed the story. They say that the Germans have the camera, and are tickled to death about it. To make sure that they don't lose it again, they'

ve built a special machine to carry it, and that machine is now operating over our Lines at an enormous alt.i.tude.'

'What type of machine?' asked Biggles.

Ah, that we don't know!'

'Then you don't know where it is operating, or what limit of climb it's got?'

On the contrary,' the major replied, 'we have every reason to believe that it is now operating over this very sector. The archie gunners have reported a machine flying at a colossal height, outside the range of their guns. They estimate the height at twenty-four thousand feet.'

'What!' Biggles exclaimed. 'How am I going to get up there? I can't fly higher than my Camel will go!'

'That is for you to work out. We are having a special machine built, but it will be two or three months before it is ready. Meanwhile, we have got to stop the Germans using that instrument. If we can get it back intact, so much the better. Rather than let the Germans retain it, we would destroy it: but, naturally, we should like to get it back.'

If the machine was shot down and crashed, or fell in flames, that would be the end of the camera?' Biggles queried. 'And if the crew found they were forced to land, they would throw the thing overboard, in which case it would be busted?'

unquestionably.'

Biggles scratched his head.

'You seem to have set a pretty problem,' he observed. 'If we don't shoot the machine down, we don't get the camera. If we do shoot it down, we lose it. That's what it amounts to. Puzzle how to get the camera! Bit of a conundrum, isn't it?'

'Well, there must be an answer,' smiled the major, 'because it has already been captured twice. We got it once and the Germans got it back.'

'Well, sir, I'm no magician, but I'll do my best.' 'Think it over and let me know when you've got it'

Biggles walked back to the ante-room, deep in thought.

'Let him know when I've got it, eh?' he mused. 'By James, what a nerve!'

12.

THUMBS TO NOSES!.

Later in the day a lot of cloud blew up from the south and west, and as this would, he knew, effectually prevent high alt.i.tude photography, Biggles did no flying, but roamed about the sheds trying to find a solution to the difficult problem that confronted him.

Finally, he went to bed, still unable to see how the impossible could be accomplished.

He was still in bed the following morning - for Mahoney was leading the dawn patrol - when an orderly-room clerk awakened him by rapping on his door and handing in a message.

Biggles took the strip of paper, looked at it, then leapt out of bed as if he had been stung.

It was from the Operations Office, Wing Headquarters, and was initialled by Major Raymond.

'High alt.i.tude reconnaissance biplane crossed the Lines at seven-twenty-three near Bethune,' he read.

That was all. The message did not state that the machine was the machine, but the suggestion was obvious. So pulling a thick sweater over his pyjamas and hastily climbing into his flying-suit, he made for the sheds without even stopping for the customary cup of tea and a biscuit.

He fumed impatiently in the c.o.c.kpit of his Camel until the engine was warm enough to take off, and then streaked into the air in the direction of the last known position of the enemy machine.

While still some distance away from Bethune he saw two S.E.5's climbing fast in the same direction, but paid no further heed to them, for he had also seen a long white line of white archie bursts making a trail across the blue of the early morning sky.

By raising his goggles and riveting his eyes on the head of the trail of smoke, he could just see the tiny sparks of white light from the blazing archie as the gunners followed the raider, who was, however, still invisible.

'By James, he's high, and no mistake!' thought Biggles, as he altered his course slightly, to cut between the hostile machine and the Lines, noticing that the two British S.E.5's carried on the pursuit on a direct course for the objective.

Five minutes later, at fifteen thousand feet, he could just see the Hun, a tiny black speck winging slowly through the blue just in front of the nearest archie bursts. Another ten minutes pa.s.sed, during which time he added another two thousand feet to his alt.i.tude, and he could then see the machine plainly.

'That plane came out of the Halberstadt works, I'll bet my shirt!' he mused, as he watched it closely. 'There is no mistaking the cut. Well, I expect that's it!' he declared, as the terrific height at which the machine was flying became apparent. He had never seen an aeroplane flying so high before, and from the major's description it could only be the special photographic plane.

It did not take him long to realize that any hopes he may have had of engaging it in combat were not to be fulfilled, for although he could manage twenty thousand feet, the enemy plane was still a good two thousand feet above him.

To his intense annoyance, it actually glided down a little way towards him, and he distinctly saw the observer produce a small camera and take a photograph of him.

'That's to show his pals what a lot of poor b.o.o.bs we are, I suspect!' Biggles muttered, and then a slight flush tinged his cheeks as the observer leaned far out of his c.o.c.kpit and put his thumb to his nose to express his contempt.

'So that's how you feel, is it, you pudding-faced sausage guzzler?' snarled Biggles. 'That'

s where you spoil yourself. I'm going to get you, sooner or later, if I have to sprout wings out of my shoulder-blades to do it!'

An S.E.5 sailed across his field of view, nose up and tail dragging at stalling-point as the propeller strove to grasp the thin air. As he watched, the machine slipped off on to one wing and lost a full thousand feet of height before the pilot could recover control.

He recognized the machine as Wilkinson's, from the neighbouring squadron, and could well imagine the pilot's disgust, for it would take him a good twenty minutes to recover his lost height.

ugh, it's perishing cold up here!' he muttered, as he wiped the frost from his windscreen, and then turned his attention again to the Hun, who was now flying to and fro methodically in the recognised manner of a photographic plane obtaining strip photographs of a certain area. Looking_ down, Biggles saw that it was over a large British rest-camp.

I'd better warn those lads when I get back that they are likely to have a bunch of bombs unloaded on 'em tonight,' he thought, guessing that before the day was out the photographs now being taken by the black-crossed machine would be in the hands of the German bomber squadrons.

'Well, I suppose it's no use sitting up here and getting frost-bitten,' he continued morosely, as he saw the S.E. abandon the chase and begin a long glide back towards its aerodrome. 'Still, I'll just leave you my card.'

He put his nose down to gather all the speed possible, and then, pulling the control-stick back until it touched his safety-belt, he stood the Camel on its tail and sprayed the distant target with his guns. He was still at a range at which shooting was really a waste of ammunition, but he derived a little satisfaction from the action. The Camel hung in the air for a second, with vainly threshing prop, and a line of tracer bullets streaked upwards.

The enemy observer apparently guessed what Biggles was doing, and called the pilot's attention, but he did not bother to return the fire. As one man, pilot and observer raised their thumbs to their noses and extended their fingers.

Biggles' face grew crimson with mortification, but he had no time to dwell on the insult, for the nose of the Camel whipped over as it stalled viciously, and only the safety-belt prevented him from being flung over the centre section. From the stall the machine went into a spin, from which he could not pull it out until he was down at eighteen thousand feet.

For a moment he thought of going over the Lines in search of something on which to vent his anger, but the chilly atmosphere had given him a keen appet.i.te, and he decided to go home for some breakfast instead, and he turned his nose towards Maranique.

Looking back, he could still see the enemy pilot pursuing his leisurely way.

After a quick breakfast, he returned to the sheds, and called Smyth, his flight-sergeant, to one side.

'Now,' he began, 'by hook or by crook, I've got to put three thousand feet on to the limit of climb of this plane!'

The N.C.O. opened his eyes in surprise, then shook his head.

'That's impossible, sir,' he said.

I knew you'd say that,' replied Biggles, 'but it's only because you haven't stopped to think. Now, suppose some tyrant had you in his power and promised to torture you slowly to the most frightful death if you couldn't put a few more feet on to the alt.i.tude performance of a Camel plane, what would you say?'

The flight-sergeant hesitated.

Well, in that case, sir, I believe -'

'You don't believe!' retorted Biggles. 'You know jolly well you'd do it; you'd employ every trick you knew to stick those extra few feet on. Very well; now let us get down to it and see what we can do. First of all, what weight can we take off her? Every pound we take off means so many feet extra climb - that's right, isn't it?'

'Quite right, sir.'

'Well, then, first of all we can take the tank out and put a smaller one in holding, say, an hour's petrol. Instead of carrying the usual twenty-six gallons, I'll carry ten, which should save about a hundred pounds, for a rough guess. That means I can climb faster from the moment I take off. All the instruments can come out, and I can cut two ammunition-belts to fifty rounds each.

If I can't hit him with a hundred rounds, he deserves to get away. If you can think of anything else to strip off, take it off. Talking of ammunition reminds me that I want the cut belts filled with ordinary bullets, not tracer bullets - I don't want to set fire to anything. So much for the weight. Now, can you put a few more horses in the engine?'

I could, but I wouldn't guarantee how long it would last.'

'No matter - do it. If it will last an hour, that's all I want. And you can get some fellows polishing up the struts and fabric - and the prop. Skin friction takes off more miles an hour than a lot of people imagine.

Now, is there any way that we can tack on some more lift? It isn't speed I want, it's climb. And do you think we could build extensions on the wing-tips? Every inch of plane-surface helps.'

If we did,' answered the flight-sergeant, 'the machine would be a death-trap; they'd come off at the slightest strain.'

'Still, it could be done.'

The flight-sergeant thought hard for a moment.

I'll take the fabric off and look at the main spar,' he said quickly. 'I've got two or three old wings about, so I should have material. I'm afraid the extensions would break away, though, or pull the whole plane clean off. The C.O. - '

'Don't you say a word about this to the C.O. He'd want me to go down to the repair depot, and you know what they'd do - they'd just laugh their silly heads off. Well, you have a shot at it, flight-sergeant - I'll give you until tomorrow morning to finish.'

'Tomorrow morning! It would take two or three days to do, even if it is possible!'

Biggles tapped him on the shoulder.

I shall be along at sparrow-chirp tomorrow morning, and if that kite isn't ready to fly, and, what is more, fly to twenty-three thousand feet up, someone will get it in the neck!'

'Very good, sir,' replied the flight-sergeant grimly. He had been set a difficult task -almost an impossible one; but he knew when Biggles spoke in that tone of voice it was useless to argue. He got busy right away.

And Biggles walked briskly back to the mess.

13.

WHAT A BULLET DID.

True to his word, Biggles strode across the dew-soaked turf towards the sheds the following morning as the first grey streak appeared in the eastern sky, having already rung up Wing Headquarters and asked that he might be informed at once if the high-flying German photographic machine was observed to cross the Lines within striking distance of Maranique.