The spare wheel was put on at last, in place of the one with the punctured tyre, and Uncle David and Mavis and Merle got into the car, and started off on to the moors. It had been quite clear in Durracombe, though not sunny, but directly they were up amongst the peat and heather great white clouds came rolling across the road, and in a few moments they were in the thickness of a white Devonshire mist. It was possible to see only for about a space of ten feet all round them. The doctor drove slowly, sounding his horn to warn anybody who might be approaching either in front or from behind. "I didn't think we should have caught a mist to-day," he commented. "I'd have started earlier if I'd known it was going to be like this. Curious how these queer fogs come on. I suppose it's our nearness to the sea. It's a regular winding-sheet. No use turning on the lamps, for they don't help. What's that! G-r-r-r! Great Scott! I believe we've got another puncture!" The unmistakable jarring sensation that betrays mishap to a tyre brought Dr. Tremayne to a sudden standstill. He got out to inspect. "Yes, it is! And the spare wheel, too! Of all the hard luck. I shall have to set to work and mend it. And here in the midst of all the fog. It might have kept up till we'd reached the farm. This is the second puncture this afternoon." "I'm afraid I'm the Jonah," said Merle. "I've had a pixie day ever since I got up this morning. Every single thing has gone wrong. I believe in bad luck, especially if you start badly. You'd better throw me overboard." "We must get started again before we can throw anybody overboard." "Can we help you, Uncle?" asked Mavis. "No, dear, not just at present. It's a question of finding the puncture. Ah! Here it is! And, would you believe it? another bit of broken glass! Some wretched tourist has been picnicking up here, I suppose, and smashed a ginger-beer bottle. Well, now I've found the spot, I can get to work." It was rather cold standing in the midst of the fog watching Uncle David. The girls began to walk up and down the road instead while they waited for him. They could see a patch of heather on either hand, and occasionally, looming through the mist, the dark body of a mountain pony or a bullock. Quite close to them, on the top of a small mound, was a little old, old worn cross, and they naturally stepped aside to look at it. Perhaps it marked some traveller's grave, or had been part of a shrine in long-ago times. Standing by its shaft they could make out through the fog another cross only a short distance away. It seemed a pity not to inspect this also. It was a far finer one than the first, and they walked all round it; then because they thought they spied a cromlech on the top of another mound they set off to inspect that too. It was not a cromlech after all, only a pile of boulders, so they turned back again. "Here we are at cross number two," said Merle.