The truth is that the wilderness of the Scottish Highlands is not easy to penetrate. You can drive through, even stop at the roadside in a "lay-by" and gaze at gloomy mountains shooting up into clouds from the further shore of a sheet of gray water. But there is a difficulty about going farther for the casual family tourist who is not a mountaineer. Even the roads are few and far between, mere threads on the map crossing empty spaces, insignificant incursions on the barrenness and secrecy between.

Stand on the summit of one of those wild ranges, close to the clouds, with moor and loch and jagged peaks outspread as far as the eye can see in every direction, and you find that all the works of man have vanished utterly, are not to be seen, neither roads nor castles nor hotels, nor even the steep-sided valleys such trivia is clustered into. The eye of the deer-stalker on the tops of the hills passes clear over them all as if they had never existed. A tourist on the road, looking up, feels this insignificance. He feels ignored, and rather crushed, standing by his automobile in the rain.

It was in the West Highlands that I realized a general truth about these vast and empty spaces, perhaps about all accessible widernesses.

There is a famous garden here, Inverewe, that is open to the public. Stopping last summer to put in an hour or two between early morning arrival at Inverness and appearance at the lodge where I was expected in the evening for a week's salmon fishing, I found the car-park packed tight with buses and automobiles -- perhaps 30 buses and 200 autos. A crowd in the garden was to be expected, and the building through which you enter was indeed densely crowded. You could hardly move.

As I pushed through the parties of tourists who were buying, or thinking of buying, the infinite variety of Scottish-associated goods with which the shop shelves were filled, I wondered if it was worthwhile going into the garden at all, so tight-packed did it promise to be. I looked through a steamy window. From the nearby restaurant, where a long queue waited, came the clatter of dishes and a smell of fish and chips, which brooded over the gravel paths leading to the plain stone house above the estuary.

But there were fewer people on the paths than I had expected, and I was encouraged to walk on, past the house into the garden proper, which is really an afforested promontory of 30 or 40 acres planted over the last hundred years with every variety of native and exotic shrub and tree which the Gulf Stream climate allows to flourish on that desolate northern coast.

In this real garden there was almost nobody but myself. I penetrated its depths by deserted paths winding through a jungle of brilliants, and of foliage, and of mighty trunks, and wandered under the giant rhododendrons of the Chinese mountains, until at last I came out into the wind and isolation of a headland above rocks and a breaking sea, with nothing but the Hebrides between myself and America. Here too I was alone.

Hundreds, even thousands, had "visited Inverewe" that day; yet most had not cared to penetrate what they had come to see.

The idea of a trip to the wild-places of the North appeals widely, and each year many thousands of families pack their bags and set out from populous zones, fully intending to explore those remote fastnesses of water and rock about which so much that is romantic has been told.

Once arrived in the Highlands (at Perth or Pitlochry, or another of the "tourist centers") the tourist's position is like that of the visitor to Inverewe: He leaves his coach, or locks his automobile, and looks about him in expectation, his interest and energy requiring to be focused on particular objectives. He says, in effect, "Now show me what I've come all this way to see."

Yet all there really is of the Highlands, that is visible, is a vast and dreary tract of emptiness, with rain or mist fast blotting out even that. Where are the eagles familiar in close-up from TV shows about "Our Heritage of Wild Life in the Highlands"? Where are the stags, otters, pine martens, wildcats? Where is the picturesque peasantry in plaids helping Bonnie Prince Charlie through purple heather? In short, what do you and your family focus on, once you have got to the Highlands?

If you look in the auto-park and restaurant at Inverewe, and into the shop shelves of the entrance building, you find the answer. People eat and buy things where they can stay under cover, and then they drive back to the trailer park or the hotel. What visitors buy -- books about wildlife, tweed, any article made from stags' horns -- both expresses and satisfies their curiosity about the Highlands. Similarly, the interest in gardening which brings a family to Inverewe may be satisfied by buying a packet of Inverewe seeds, and perhaps a souvenir trowel to plant them with.

There are of course ways into these hills, tracks which may be walked by anyone, by custom if not by right. Where such a track meets the high road you will see autos parked, people sitting on the trunk to pull on heavy boots and redo yellow waterproofs, the glen speckled with brightly colored groups tramping along the track, or peering into the rapid river. The arteries of the highways pump these few hectic corpuscles up the little veins of hill-tracks, but as yet the pulsations are feeble, and the corpuscles themselves often disheartened.

Nevertheless, it is these red and yellow dots in the glens which are the future inheritors of the Highlands. They are the forerunners of the lately evolved race of conquerors, Tourist Man, under whose directions all the wildernesses of the earth will one day be parceled out into Picnic Sites linked together by Nature Trails.

Out of the dun-colored wastes a good many old eyes watch them. There are the red deer and ptarmigan far up among the precipices, the wheeling eagle gone behind a crag before binoculars can be focused; and there are, too, the eyes of that older race of human beings watching them, the eyes of Hunting Man.

This once omnipotent race of visitors to Scotland, who have indeed more or less controlled the remoter Highlands for the last 130 years, are the sportsmen, with their attendant gillies and stalkers and gamekeepers. Unlike Tourist Man, the clothing of Hunting Man tends towards the subfuscs of his habitat, for his endeavor is to conceal himself from his quarry. Rather than considering how to help the Mountain Rescue team spot him if he should fall over a precipice and break his leg, he considers how to creep unseen by burn-course and peat-hag within rifle-shot of his stag.

Therefore he is not obvious afar on the hill as Tourist Man is, but will suddenly appear close at hand, surprising the camper who has dropped a line in the river with a worm on its hook -- or surprising the camper's wife who has dropped into the river without any clothes on -- an apparition of fierce old-fashioned aspect in rough dark tweeds with a cap over his eyes and dubbin on his boots, attended by a craggy Scotsman in plus fours and a deer-stalker hat. His ingrained and natural-born belief, that mountains and rivers may belong to one man with all that they contain, is hard to convey without irascibility to Tourist Man, who is used to the ownerless parks and recreational areas of the city.

Despite his bluster, Hunting Man is in retreat, a doomed species. His lair, like the eagle's nest, is in a retired glen. It is the lodges visible from public roads that were first surrendered and are now become hotels garrisoned by Tourist Man. Sporting lodges in private hands are as remote and well-concealed as the last haunts of pine marten or wildcat, at the end of many miles of private track or upon the further shores of lochs -- large stone Victorian mansions in the middle of nowhere.

There do still remain, no doubt about it, vast private kingdoms in the Highlands to this day, as blank on the tourist map as was Central Africa a century ago -- the 50,000 acres of a Knoydart or an Apple-cross lying behind their own ranges of mountains, seagirt kingdoms where Hunting Man makes his last stand.

It is in fringe territory, where the two interests of tourism and hunting overlap, and a moral skirmish -- if not a physical one -- is likely to result from a meeting of the two races.

A few days after my visit to Inverewe I had been fishing the river owned by my host's family at a point three or four miles into the hills, where a narrow pass confines its flow to a torrent roaring over huge boulders between pools of black water.I had hooked a salmon in one of these pools. It was away in a flash over some falls, and I was obliged to scramble after it -- in and out of the ranging water or edging along a rock ledge high above it -- until the fish would stand and fight.

At last I killed it, and scrambled up through the birch and rock of the gorge to a track where I could leave the fish under a cairn of stones to be picked up by a gillie. As I appeared out of the gulf -- soaked to my waist, well daubled with peat and flecked very likely with the blood of the salmon I grasped by its gills -- a family of tourists happened to be walking along the track. Very naturally they shrank from me, and the younger children burst into tears.

Even when alarm had subsided, and cameras had been extracted from brilliantly colored anoraks to photograph this apparition of Hunting Man burst from his watery depths, they were not friendly. It was with pursed lip and chilly eye that they viewed a barbarian so unreformed by wildlife programs on TV -- so impious of the new religion -- that he would desecrate a Region of Outstanding Natural Beauty by killing a fish for fun.

And I was affected by their disapproval. I felt a twinge of conscience I would never have felt 20 years ago, as though I had been caught in the garden at Inverewe with the trunk of tricuspidaria lanceolata over my shoulder and a buzz saw in my hand. How that ferocious old sportsman Osgood Mackenzie, who first planted a garden at Inverewe 120 years ago, would have sneered at my qualms! But then, he would not have credited the pressures upon Hunting Man. It would have been to him beyond all bounds of possibility, that 120,000 tourists a year would one day visit his garden. CAPTION: Illustration, no caption; Photo, Eilean Donan Castle, at Dornie on the west coast of the Highlands, BY JIM BRANDENBURG, (c) 1985 NATIONAL GEOGRAPHIC SOCIETY