The spectators at steamy Capital Centre were treated to free pennants and a free sauna last night. The ice did not melt, however, and neither did the Boston Bruins, who clinched the Adams Division title for the fourth straight season by thrashing the Capitals, 4-1.

"Tonight was one of the best games we've played in along time," enthused Boston Coach Don Cherry. "It was the most important game of the season for us. We had to win this game to clinch it all and we wanted to win it on the road."

Terry O'Reilly collected two goals for the Bruins, who produced three scores on power plays in a penalty filled game that saw two players, Boston's Stan Jonathan and Washington's Yvon Labre, ordered to early but probably welcome showers.

"Everybody worked hard, but we just came up short," said Washington Coach Danny Belisle. "There'no mystery about it. We played as well as we can play, but obviously the injuries are showing."

If the Capitals can play no better, they are due for a tough time again tonight, since the 7:30 visitors to Capital centre are the potent New York Islanders (16-0-3) share the coomon attribute of never having lost a game to Washington, winless in its last 10 starts.

The Capitals gave their supporters in the divided house of 16,938 a lift when Mark Lofthouse, called back yesterday from Hershey, opened the scoring on a power play 3:27.

Such quick results might have been termed a nuclear reaction, since Loft house was coming from Three Mile Island territory and a sign over his locker read, "Danger: radiation. Please stay away."

After Ryan Walter was chased for cross-checking O'Reilly, Boston's more potent power play reacted quickly and tied it, with Wayne Cashman blasting a 50-footer through goalie Jim Bedard.

Then came the easily discernible turning point. Cashman hauled down Washington's Robert Picard, who embellished his fall to the extent that referee Dave Newell diagnosed dive and declined to call a penalty.

Reserve goalie Gary Inness then called Newell an unpleasantry and Washington was slapped with a bench minor, facing a penalty-killing situation instead of a power play.

"It was nothing 12 other guys weren't calling him,..said Inness, who admitted it wasn't printable, either.

Nine seconds later, Jean Ratelle's 15-footer from the slot slithered off Bedard's right pad inside the post and Boston was ahead to stay.

Boston made it 3-1 when Washington's Gord Lane put the puck on O'Reilly's stick in the slot. Then O'Reilly converted Cashman's pass from the corner to wrap up the scoring. There was still plenty of action to keep the fans sweating, however, and most of it centered around the Capitals' Dennis Hextall.

Hextall and the Bruins have a history of discontent dating back six years to a war between Hextall and Cashman. It was accelerated last year when Hextall rammed Boston's Gary Doak into the glass, causing severe facial injuries. Then this season the Bruins pursued Hextall all over the ice in their first meeting with his old Detroit club.

So it was no surprise that Boston goalie Gerry Cheevers jabbed Hextall with his stick and Hextall responded with a glove in the Goalie's face. That brought several Bruins in Hextall's direction and it was Lady Byng candidate Peter McNab who got there first, shoving Hextall into the boards.

After minor penalties to Hextall and Cheevers had expired, Jonathan ambushed Hextall with an elbow and started punching him. Hextall covered up and Labre and Paul Mulvey came to his aid. Hextall went unpenalized, Labre was chased as the third man in the altercation and Jonathan was assessed a minor, a major and a pink slip.

That presented Washington with the prospect of a seven-minute power play, since Jonathan's stand-in, Cashman, could not leave the box after any goals scored during the first five minutes.

Cherry objected strenuously to that arrangement, but he needn't have bothered. The Capital's power play, minus injured stalwarts Tom Rowe and Bob Sirois, managed only two harmless shots in 4 1/2 minutes and the advantage disappeared when Mulvey was penalized for hooking Brad Park.

"I've had a lot of trouble with that club", Hextall said. "They have an agressive club and I have to be ready for them. But I know they're coming and I know I can suck them into penalties. It's just that we couldn't capitalize on it tonight. A couple of goals would have got us back into it."