THERE IS something essentially primal about the Adirondack Mountains. Maybe it's because their peaks, unlike the bald crests of the Alps and Rockies, are dark with evergreens that march uninterrupted down to the rim of the icy lakes at their feet. Any of these lakes could be the setting for "An American Tragedy" - Moose Lake actually was - and the eerie cry of the loons that lvie on them strikes straight to the heart. The Adirondacks are close in, blue-hazed and beautiful, and it's hard to shake the feeling that here at last is a place where nature still keeps the upper hand and it is best to guard the matches and keep to the path.

The Adirondacks are one of our last unspoiled with areas, the largest east of the Mississippi, and the credit for this belongs to the state of New York, which almost 100 years ago recognized its treasure and drew an invisible blue line around 6 million acres of north country wilderness and decreed that it should be henceforth forever wild.

No four-lane highways feed intot he Adirondacks; few billboards or ticky-tacky dinner deface them. The Adirondacks are remarkably unchanged since the end of the 19th century when W.H.H. Murray wrote a guidebook describing the region and the first visitors, known then as Murray's Fools, came by rail and stage to taste its wonders.

In winter this is harsh, forbidding country, a land locked in snows for eight months of the year. Iceusually leaves the lakes the last week in May; in Saranac Lake, near the northern border, 40 below for days at a time is not uncommon.

Saranac Lake was once a place where many feared to come. Known as the "City of Sick," it was a center for TB cure where the country's most famous specialists practiced. In the 1920s, its population of 6,000 absorbed an influx of more than 1,500 TB victims, and such was the fear of the disease in those days that many a motorist speed through the town with his handkerchief over his nose and the accelerator to the floor. The discovery of wonder drugs after World War II returned Saranac to its former sleeping status, but you can still see the sleeping porches built on nearly every house for invalids taking the air.

It is possible to drive the main road between Saranac and Tupper Lake at night and see no more than a light or two on the entire 25-mile stretch. This wilderness area is larger than Yosemite, Yellowstone, Olympic, Glacier and Grand Canyon National Parks combined, and being alone in it at night for city folk can be an experience.

But skis and bobsleds have made the Adirondacks a winter playground and it is, at any time of year, a sportman's paradise. Forty thousand campsites are maintained here in unspoiled woods for huntsmen, fishermen or people who just want to lean back in a sleeping bag at night and see that stars unsmudged with urban smog, or catch a glimpse of deer, mink, otter or fox.

The chamber of commerce in any of the cities in the preserve will provide a guide to mountain trails. The New York State Department of Commerce would be pleased if you would try some of the 42 other peaks instead of Mt. Marcy, the 5,344-foot-high mountain that is beginning to show signs of wear from the feet of thousands of visitors who want to scale the Mt. Everest of New York State. Baker Mountain will give you a bit of a challenge; Mt. Pisgah is a short, easy climb; and if you really can't do without your car, you can go to the top of White-face without leaving the driver's seat.

The two narrow roads feeding into the park will be full of campers this season, but if you cling to the idea that cmaping means tents or lean-to's, write to the Department of Environmental Conservation, State Campus, Albany, N.Y., for a list of places the mechanized campers leave for people like you. A number of them lie at the end of winding dirt roads just off the highway, manned by rangers who will ask you to register before setting off.

This is true wilderness, and every summer visitors wander off the trail and are lost in the woods. It's easy to drift off a blazed trail onto one beaten down by animal feet leading nowhere in particular. The feet may well belong to bears, though they are more inclined to the civilization of a garbage dumps. Still, a recurring subject of conversation in the north country is how to behave when you meet a tsmen from New York City used to come north on the railroads to set the fashion for Adirondack vacations, and a nostalgic peek back into the land they found is at Blue Mountain Lake in the Adirondack Museum. This is a small gem of a regional museum, dedicated to man's relationship to the Adirondack wilderness, a gentle celebration of a rugged life that disappeared with the coal stove and the horse. You find it all preserved here, from the stuffed chipmunk penwipers and fungus art of J.P. Morgan's "camp" to the little cabin in which Noah Rondeau spent 42 years as a hermit. And you shouldn't miss the exhibit of guide boats, those indigenous handcrafted boats now rapidly passing into history, which once were used for everything from courting to grocery shopping.

Those two two-lane roads into the perserve will be bumper to bumper in 1980, when Lake Placid hosts the Olympics, and every hotel and motel from Malone to Old Forge is already sprucing up. The Lake Placid Club, once a private, members-only enclave, is now open ot the public and has added a new cocktail lounge. The club was built in the 1890s when private railroad cars were still bringing the rich from the city and whole families arrived with nursemaids, children and a gaggle of trunks.

A restless new generation preferred to go elsewhere and the storied old grande dame has reopened her doors to transients, including convenctions. This is a resort hotel set plunk in the middle of the most gorgeous mountain scenery in the state and it is expensive; dinner for two is $23.

If you're watching pennies the Hotel Saranac, at Saranac Lake 10 miles away, is a real bargain. Built in 1926 by the famous New York architect William Scopes, its lobby is a replica of a 15th-century Venetian reception room with decorated exposed beams and a wonderrful old outsize stone fireplace. The Paul Smith College, which trains hotel personnel, owns it now, and except for a few professional advisers, the place is run entirely by 17-and 18-year-olds doing a term in field work. Sixteen dollars will buy a room for two and the young people will knock themselves out to take care of you.

This is not to say that everything works like clockwork. On a recent trip, en route from my room to the lobby, I shared the elevator with a gentleman attired in pajamas and slippers. "Please overlook it," he implored, "but I've been trying to get the desk for the past 15 minutes."

New York State officials are deemphasizing the Lake Placid area a acommodations (which includes Saranac) for Olympic spectators, because they will be needed for persons connected with the Olympics. Every room will be booked, they say, so the public should look as far away as Malone or even Glens Falls. New York State is expecting 80,000 people a day at Lake Placid, at Mount Van Hoevenberg, seven miles east on Rte. 73, and at Whiteface, six miles north on Rte. 86. Officials are even planning to reactivate the railroad, which runs from New York City to Old Forge and hasn't carried passengers since the 1960s.

It might not be a bad idea to see those mountains before the onslaught. The black flies are gone by late July. Just watch for chipmunks on the road.