'Yes, we could,' said George eagerly, 'I'm longing to get down there and Make Discoveries!'

'Well, let's have something to eat first,' said d.i.c.k. 'It's long past our dinner-time. It must be about half-past one. Yes, it is!'

'George and I will get you a meal,' said Anne. 'We called at the farm on our way up and got a lovely lot of food. Come on, George.'

George got up unwillingly. Timmy followed her, sniffing expectantly. Soon the two girls were busy getting a fine meal ready, and they all sat on the rocky ledge to eat it.

'Mrs Mackie gave us this enormous bar of chocolate for a present today,' said Anne, showing a great slab to d.i.c.k and n.o.bby. 'Isn't it lovely? No, Pongo, it's not for you. Eat your sandwiches properly, and don't grab.'

'I vote we take some food down into the hill with us,' said Julian. 'We may be quite a long time down there, and we shan't want to come back at tea-time.'

'Oooh - a picnic inside the hill!' said Anne. That would be thrilling. I'll soon pack up some food in the kitbag. I won't bother to make sandwiches. We'll take a new loaf, b.u.t.ter, ham and a cake, and cut what we want. What about something to drink?'

'Oh, we can last out till we get back,' said Julian. 'Just take something to eat to keep us going till we have finished exploring.'

George and n.o.bby cleared up and rinsed the plates. Anne wrapped up some food in greased paper, and packed it carefully into the kitbag for Julian to carry. She popped the big bar of chocolate into the bag, too. It would be nice to eat at odd moments.

At last they were all ready. Jimmy wagged his tail. He knew they were going somewhere.

The five of them pushed the caravan back a few feet to expose the hole. They had all tugged the van back into place the night before, in case Lou and Dan came to go down the hole again. No one could get down it if the caravan was over it.

The boards had been laid roughly across the hole and the boys took them off, tossing them to one side. As soon as Pongo saw the hole he drew back, frightened.

'He's remembered the darkness down there,' said George. 'He doesn't like it. Come on, Pongo. You'll be all right. We've all got torches!'

But nothing would persuade Pongo to go down that hole again. He cried like a baby when n.o.bby tried to make him.

'It's no good,' said Julian. 'You'll have to stop up here with him.'

'What - and miss all the excitement!' cried n.o.bby indignantly. 'I jolly well won't. We can tie old Pongo up to a wheel of the van so that he won't wander off. Lou and Dan are away somewhere, and no one else is likely to tackle a big chimp like Pongo. We'll tie him up.'

So Pongo was tied firmly to one of the caravan wheels. 'You stay there like a good chimp till we come back,' said n.o.bby, putting a pail of water beside him in case he should want a drink. 'We'll be back soon!'

Pongo was sad to see them go - but nothing would have made him go down that hole again! So he sat watching the children disappear one by one. Timmy jumped down, too, and they were all gone. Gone on another adventure. What would happen now?

CHAPTER EIGHTEEN

INSIDE THE HILL

The children had all put on extra jerseys, by Julian's orders, for he knew it would be cold inside the dark hill. n.o.bby had been lent an old one of d.i.c.k's. They were glad of them as soon as they were walking down the dark pa.s.sage that led to the first cave, for the air was very chilly.

They came to the small cave and Julian flashed his torch to show them where the footholds went up the wall to a hole in the roof.

'It's exciting,' said George, thrilled. 'I like this sort of thing. Where does that hole in the roof lead to, I wonder? I'll go first, Ju.'

'No, you won't,' said Julian firmly. 'I go first. You don't know what might be at the top!'

Up he went, his torch held in his mouth, for he needed both hands to climb. The footholds were strong nails driven into the rock of the cave-wall, and were fairly easy to climb.

He got to the hole in the roof and popped his head through. He gave a cry of astonishment.

'I say! There's a most ENORMOUS cavern here - bigger than six dance-halls - and the walls are all glittering with something - phosph.o.r.escence, I should think.'

He scrambled out of the hole and stood on the floor of the immense cave. Its walls twinkled in their queer light, and Julian shut off his torch. There was almost enough phosph.o.r.escent light in the cavern to see by!

One by one the others came up and stared in wonder. 'It's like Aladdin's cave!' said Anne. 'Isn't that a queer light shining from the walls - and from the roof, too, Julian?'

d.i.c.k and George had rather a difficulty in getting Timmy up to the cavern, but they managed it at last. Timmy put his tail down at once when he saw the curious light gleaming everywhere. But it went up again when George patted him.

'What an enormous place!' said d.i.c.k. 'Do you suppose this is where the men hide their stuff, whatever it is?'

Julian flashed his torch on again and swung it round and about, picking out the dark, rocky corners. 'Can't see anything hidden,' he said. 'But we'd better explore the cave properly before we go on.'

So the five children explored every nook and cranny of the gleaming cave, but could find nothing at all. Julian gave a sudden exclamation and picked something up from the floor.

'A cigarette end!' he said. 'That shows that Lou and Dan have been here. Come on, let's see if there's a way out of this great cave.'

Right at the far end, half-way up the gleaming wall, was a large hole, rather like a tunnel. Julian climbed up to it and called to the others. 'This is the way they went. There's a dead match just at the entrance to the tunnel or whatever this is.'

It was a curious tunnel, no higher than their shoulders in some places, and it wound about as it went further into the hill. Julian thought that at one time water must have run through it. But it was quite dry now. The floor of the tunnel was worn very smooth, as if a stream had hollowed it out through many, many years.

'I hope the stream won't take it into its head to begin running suddenly again!' said George. 'We should get jolly wet!'

The tunnel went on for some way, and Anne was beginning to feel it must go on for ever. Then the wall at one side widened out and made a big rocky shelf. Julian, who was first, flashed his torch into the hollow.

'I say!' he shouted. 'Here's where those fellows keep their stores! There's a whole pile of things here!'

The others crowded up as closely as they could, each of them flashing their torch brightly. On the wide, rocky shelf lay boxes and packages, sacks and cases. The children stared at them. 'What's in them?' said n.o.bby, full of intense curiosity. 'Let's see!'

He put down his torch and undid a sack. He slid in his hand - and brought it out holding a piece of shining gold plate!

'Coo!' said n.o.bby. 'So that's what the police were after last year when they came and searched the camp! And it was hidden safely here. Coo, look at all these things. Jumping Jiminy, they must have robbed the Queen herself!'

The sack was full of exquisite pieces of gold plate - cups, dishes, small trays. The children set them all out on the ledge. How they gleamed in the light of their torches!

'They're thieves in a very big way,' said Julian. 'No doubt about that. Let's look in this box.'

The box was not locked, and the lid opened easily. Inside was a piece of china, a vase so fragile that it looked as if it might break at a breath!

'Well, I don't know anything about china,' said Julian, 'but I suppose this is a very precious piece, worth thousands of pounds. A collector of china would probably give a very large sum for it. What rogues Lou and Dan are!'

'Look here!' suddenly said George, and she pulled leather boxes out of a bag. 'Jewellery!'

She opened the boxes. The children exclaimed in awe. Diamonds flashed brilliantly, rubies glowed, emeralds shone green. Necklaces, bracelets, rings, brooches - the beautiful things gleamed in the light of the five torches.