NO DOUBT there is a ski area operator somewhere who delights in summer, who loves to see his costly machinery at rest, who likes the silence of an empty mountain.

But for every such one there must be 1,000 who curse the vagaries of climate and weather, who knit their brows in harried pursuit of something, anything , to do with that pile of useless earth once the snow melts.

Enter the Asco Corp. of Bromley, Vt., purveyors of snake-like troughs of snow-white absestos which thrive on heat and which can be installed, at monumental cost, on anybody's mountain. Once in place they are the answer to the summer ski-lift dilemma.

It's called the Alpine Slide and it gives people the reason they need to go up someone else's hill: a hair-raising way back down.

This year there are Alpine Slides at three ski mountains close to Washington where last year there were none, which says something about the appeal of this treat for the escapist. All three are in Pennsylvania, at Camel back (Tannersville), Seven Springs (Somerset) and, closet of all, Ski Liberty near Gettyburg.

Alpine slides are a totally new phenomenon. According to Adi Richter, the manager at Liberty, they originated three or four years ago in Gevelshausen, West Germany, with a 400-foot model. The folks at the Bromley ski resort heard about it and and went for a look. When they came back they decided to do it up. American style.

The result was a 4,000-foot monster that "took off" in popularity , Richter said. Today there are 15 slides across the country, and liberty and Camel-back rate with the big ones at 3,400 feet. Seven Springs is smaller, about 1,800 feet.

The slides come about as close to an Olympic toboggen run as you're likely to get on a hot summer day in Pennsylvania. They are built of slick concrete and asbestos, then sanded and finished with wax to provide a super-slippery course. Speeds of up to 45 m.p.h. are possible.

The run at Liberty is dotted with high-banked turns and one heart-stopping jump. It is not without danger, as Richter explained: "People are pretty cautious the first time through. After that they try to go faster. Americans are quite competitive, as you know."

The sleds offer very little protection. They are plastic, about three feet long, and the nuts and bolts are minimal. It comes down to two options, fast or slow.

The rider has a stick control. Push it forward and the little car rocks up on two hot wheels about two inches across; pull it back and it plunks down on four rubber stopper pads, like bicycle brakes. If you leave the stick alone you slide wildly on four sharp runners. Generally, riding the runners all the way is sheer chaos; they provide no grip and the sled swerves up and down and eventually out of the banking.

Going over the top can be unpleasant. According to Rick Lombard, who helps operate the Liberty slide, one wildman flipped out and cut off the tip of a finger; other are more fortunate and end up with only singed skin.

"When they blow out you can hear the skin burning when they slide along the track," Lombard said.

The skin-burners are generally crazy teen-agers who need the lesson, anyway. But the super-safety-conscious can suffer, too. Some folks are so cautious they bring their sleds to a halt halfway down. This is fine if they get out in a hurry, but on busy weekends there's always the chance of a hotrodder hard on your tail, and crashes do not tickle.

At Liberty the cost of a downhill plunge is $2.50, or $2 for youngsters, including a quick lesson at the top. Rates are cheaper if you buy a book of 10 or more rides. Liberty sold 3,000 rides in one day over the Labor Day weekend but things are slowing down now and the seven-days-a-week policy has been dropped back to weekends only.

One caution: Don't bother to head for the hills if there's a chance of rain. Water on the rack stops all activity immediately.

Half the fun for old stick-in-the-muds like me is the ride up. Nonskiers finally get a chance to see the world from a chairlift, and there are not many prettier places to spend 12 minutes than gliding up a rural Pennsylvania mountain in the height of fall.

There's only one problem - once the snow starts to fall the Alpine Slide is useless and has to be shut down. Which must drive the Alpine Slide operators nuts. . . .