A row of prehistoric stones forms one of the three Hurlers circles — so-called from the legend that they were once rebellious sportsmen — in Bodmin Moor in Cornwall. (John Husband / Alamy)

A sheep was casually scratching its butt against a rough stone, a rural English picture from time immemorial. Like, say, a few millennia. The stone was actually set upright in this convenient sheep-scratcher position some 3,000 years ago, give or take a few centuries, one of 24 arranged for some lost Bronze Age ritual.

This is the Brisworthy Stone Circle.

The which?

Everyone knows about Stonehenge, the majestic stone edifice 36 yards in diameter, its tallest monoliths 30 feet high, some crossed with lintels like giant doorways. Dominating Salisbury Plain in brooding isolation, the site has aroused wonder and speculation for centuries. Why was it built? We don’t know. How did they get some of the stones all the way from Wales? We don’t know. Were Druids involved? That we do know. No. (Stonehenge is 3,000 years too early for the Druids.)

If you go: Britain’s stone circles

Think of Brisworthy Circle, then, as . . . well, maybe not Bride of Stonehenge.

Son of Stonehenge? . . . Er, not exactly.

Nephew of Stonehenge? Closer. . . .

Third Cousin Once Removed of Stonehenge?

That’s the one. Brisworthy is little. Though the diameter is roughly 27 yards, the stones range from only about two to five feet tall — I sat on one to watch the sheep.

I was in the middle of a pasture in Dartmoor, the bleak Devon moorland made famous in “The Hound of the Baskervilles,” and I’d had some trouble getting here. For anyone interested in visiting the smaller stone circles of Britain, you should know that many of them aren’t particularly easy to find, being at the end of footpaths that begin at obscure spots on narrow, hedgerowed minor roads. My advice to would-be circle finders is to get the largest-scale Ordnance Survey map you can and ask for lots of directions. (Do not believe the words “You can’t miss it.” You can and you will.)

I’d wandered through at least three fields, trying to avoid sheep droppings and wondering a little wildly whether I might miss the circle, because Dartmoor, let me tell you, is full of rocks. Slabs of them lie casually about, as if napping.

I became uncertain. I knew that until a century ago, most of the stones had lain collapsed on their sides; they were set up again in 1909 by two amateur antiquarians (one a vicar). Perhaps they had fallen again? Maybe I was a mile from where I should be. Maybe the field’s owner, sick at last of clueless roaming tourists, would pop up with a shotgun held casually crooked under his arm —

Then there it was. Among the scatter of boulders stood a precise little construction, as uncannily out of place as a UFO. It was purposeful, deliberate and completely inexplicable. The scratching sheep didn’t matter. The small size didn’t matter. I felt awe.

Secrets of the circles

There are approximately 1,300 stone circles in the British Isles. Actually, if you count the ones that surround burial cairns, there are maybe two or three times that number, but let’s not go there; 1,300 is plenty. There are clusters of circles in northern and southwestern Ireland, in the Highlands, in the Lake District and in Wales, but you can find them scattered across the countryside in many locations with available stone. (Where there was little rock, people built circles of wood, their sites detectable today by the surviving postholes). Dartmoor has 70-plus.

Stone circles were built from the late Neolithic period to the early Bronze Age. No one knows why. Stonehenge is so elaborate that some reasonable conclusions can be drawn about its uses (there are, for example, definite configurations for astronomical measurement). At Brisworthy, remains of millennia-old burned charcoal have been found, but it’s hard to extrapolate much from that lonely fact. The small circles — country churches to Stonehenge’s cathedral — are mute in their simplicity.

Not that stories haven’t been told about them down the centuries. Brisworthy, set in its humble field, has no legend attached, but its more accessible and celebrated Oxfordshire cousin, the Rollright Stones, has several. One claims that the number of stones in the 36-yard wide circle cannot be counted. This turns out to be true. Surveys from the 17th century onward have asserted that there are anywhere from 46 to 102; the currently accepted number is around 77.

Such delightful indeterminacy sounds like something out of a fairy tale. The prosaic truth, as I learned once I’d parked by the entry gate and walked into yet another field, is that the rocks have weathered and broken over the years like soft teeth. (Rollright is unusual in having imported its stone, and the nearest source was of friable limestone rather than granite.) Though archaeology has revealed that the stones once stood close-packed, shoulder to shoulder, today a chest-high upright may have calved a two-foot boulder that now lies comfortably next to it as if it had always been there.

The corrosion breeds confusion. Is that split stone one or two? Should you count the tiny boulder almost buried at the base of a five-footer? I walked all the way around twice, seeing whether I could come up with the same number both times. I couldn’t. Perhaps it was just as well — whoever can count them the same way three times is cursed. Or blessed, depending on the story.

In spite of the effects of centuries of exposure to weather and wind, or perhaps because of that, the circle is spooky. Its almost perfect roundness gives the sense that it sprang up all at once, like a mushroom ring. Against the stand of trees separating the field from the road, it looks both completely natural and eerily unexpected.

The subtly weird effect is enhanced by the fact that Rollright is actually a complex. Diagonally across the field from the circle, three tall megaliths lean toward one another as if in conversation — the Whispering Knights. And on the other side of the road, surrounded by an iron-spiked fence, looms the eight-foot King Stone, erected circa 1800 B.C. When I was there last summer, the King Stone had acquired a marvelous wooden twin — a tall, primitive-looking, vaguely humanoid construction of old boards and branches. Its “face,” turned toward the King Stone, was a box, in which someone had laid a yellow wildflower. Paganism lives.

Into the fog

Paganism, specifically witchcraft, is said to account for the Rollright Stones’ existence. The King (whoever he was) unwisely made a bet with a witch and lost, with the result that she turned him and all his court to rock. In contrast, the three magnificent circles that make up the Hurlers, in Cornwall, are the consequences of Christian blasphemy: playing a game on the Sabbath. In mid-throw, the irreverent sportsmen were transformed like Lot’s wife, but into granite rather than salt.

The Hurlers should have been easy to find. There were signs along the approach on the B3254, the entrance was clearly marked, and there was even a small car park from which a wide, smooth track led onto Bodmin Moor.

Unfortunately, there was also fog.

When as a child I first read “The Hound of the Baskervilles,” I was alarmed and impressed by the huge bank of fog, opaque as a wall, through which the monstrous hound suddenly and savagely burst. As an adult, I figured that Conan Doyle had used a little poetic license for atmospheric effect.

I was very, very wrong.

Okay, I could see my hand in front of my face. Probably my field of vision extended about 20 yards. But after that: white nothing. This was the only day I had to visit the Hurlers, but it wasn’t going to happen. Earlier on the trip, I had nearly tumbled off one of the high piles of rock known on Dartmoor as a tor, but I wasn’t fool enough to wander into this visual wilderness and end up dead of hypothermia less than a mile from the road, my corpse pathetically gnawed by moorland fauna.

And then — a dog burst from the fog.

Not a Hellhound, but an exuberant border collie, followed shortly by its owner, a cheerful woman in a hooded yellow rain slicker. No mere blinding fog can prevent the Englishman or woman from taking Fido walkies. Yes, she said, the Hurlers circles were just down the track. Less than half a mile. Off to the right. “Though I’m not sure,” she added with concern, “that you can spot them in this weather.”

I made a decision. I’d walk down the track for 10 minutes, which should be approximately half a mile. If in that time I didn’t find anything that resembled a stone circle, I’d turn back, and that would be that.

The track was easy to navigate, and as it turned out, I’d been walking less than 10 minutes when I saw a stone a few yards away.

Admittedly, it wasn’t the right kind of stone. It was a little cube, probably a Victorian boundary marker. Still, it was the only stone I had, so I walked over to it. And once I got there, I could see, a few more yards away, a monolith about four feet high. That seemed encouraging. Carefully, glancing back over my shoulder to be sure that I didn’t lose sight of the boundary stone, I walked to it. And from there, I could see, spectral in the mist, three stones set close together, arcing away into the fog. Once more I walked cautiously forward, and so came to the first circle of the Hurlers.

I stood in the center of the 100-foot ring, turning slowly to take in the 15 stones, three to five feet tall and softly swirled with fog. The surrounding landscape, scarred by tin mining, was hidden. The drifting mist temporarily hid a stone, then shifted to reveal it and hide another. Everything was silent, the way snowfall is silent. Was it magical? Yes, I’m sorry to have to admit: It was magical. I was standing in the middle of a cliche, and it was a great cliche. I walked around the circle, stroking the inner surface of the stones, which the Bronze Age builders had hammered smooth. When I came to the point opposite where I had entered, I could just make out bits of the second circle several more yards away.

The second circle is the largest of the three, nearly 150 feet in diameter, with 14 extant stones. (The whole site was excavated and restored in the 1930s; it is thought that each circle originally contained 29 stones.) In the middle, just slightly off-center and leaning a little, stood a granite pillar about a yard high. I stood here quietly for some time. When I moved to the far side and peered through the fog, I saw no sign of the third circle. That was all right. To ask more at this point would be asking too much.

I made my way back, from second circle to first, from there to the monolith, from the monolith to the boundary stone, from that to the road. When I looked back, all I could see was the boundary stone. Everything else had vanished.

Rose is a former Washington Post theater critic.