The fuzzy yellow ball went back and forth across the net 21 times on this particular point. On some passages, it whistled with velocity and spin. On others, it traveled in such a high, lazy are you could almost read the label.

Finally, the small fellow, his pale-blue shirt drenched and his socks stained with a red clay ring around the ankles, picked out an invitingly short shot to pounce on. It bounced up around his eyebrows. Both feet left the ground as he smacked a forehand.

This time the ball did not come back.

Harold Solomon, tennis laborer, was back at work. Sliding. Shoveling. Sweating. Digging in the trenches with his unsightly but effective strokes, winning more with perspiration than inspiration.

Yesterday, he beat lefthander Tom Gullikson, 6-4, 6-4, in the third round of the $175,000 Volvo International tournament at the Mt. Cranmore Tennis Club, a picturesque, 10,000-seat facility carved into the countryside of the White Mountains. It was Solomon's ninth victory in a row. Last week, he won the Louisville Classic, beating Phil Dent, old nemesis Manuel Orantes, Wojtek Fibak and John Alexander in the last four rounds.

Because conditions were exceptionally "heavy" yesterday - the clay moist from early morning showers, the air unusually humid for the "north country" of New England, and the Penn ball in use here slower than the Dunlop adopted for most American summer tournaments - Solomon reverted primarily to the style that characterized him several years ago.

He teased Gullikson with topspin loopers and frequent "moon balls" - lobs that floated through the muggy atmosphere in a mesmerizing parabola.

Solomon, a year younger than Gullikson at 25, rallied patiently, scampered for energetic "gets," and kept the ball in play. He waited out his opportunities for an attacking shot, opened up the court and then went for the kill.

Moon balls and other paceless junk shots prevented Gullikson from establishing any rhythm. They kept him from hitting himself into a net-rushing groove. Solomon outsteadied rather than outhit him.

"I don't usually play that way, anymore, but I do what I have to do to win. It depends on the guy I'm playing and the conditions," Solomon said after his breakfast time (10 a.m.) match.

"Today, the balls were like watermelons. It's almost like playing in Europe here - the clay is damp, soft, deep and loose on top, and the balls are heavy.

"It didn't make any sense to try and go out there and nail everything as hard as I could. I couldn't put many balls away even if I hit them all my might, and neither could be. The moon ball doesn't expend much energy, and it makes the other guy impatient. It bounces high and gives you time. It's a good tactic for these conditions."

On one critical point, however, Solomon did the unexpected. Serving for the first set at 5-4, 15-30, he followed his first serve to the net for the first time and angled away a backhand volley.

"I did the same thing last week, against Orantes. At 3-1 in the second set, I served-and-volleyed for the first time in the match," Solomon said, grinning like the canary who had swallowed a cat.

Solomon play No. 1 seed Eddie Dibbs in the quarterfinals today. He expects to be in an attacking mood against his old friend and rival, who has beaten him eight times in a row since 1974, the last five in a straight sets.

"I'll have to go for more. I don't think I can outlast Dibbs, so I'll try to put a few more balls away," Solomon said. "I hope the court dries out and plays a little faster. I think that will help me."

Two weeks ago, Solomon lost rather listlessly to Spanish Davis Cupper Jose Higueras in the quarterfinals of the Washington Star International. He wasn't much better in the first two rounds at Louisville, but struggled past Ricardo Cano and Bernard Fritz, who are not likely to be confused with Bjorn Borg and Jimmy Connors.

On the third day of the tournament, after a lackluster practice session, he told his girlfriend, Jan Lindsay. "If I don't play any better tonight against Dent, we're out of here."

He did play better. "I didn't miss a ball, and I played really well the rest of the week. I've been hitting the ball solidly, and it all clicked," he said yesterday.

Louisville provided his second tournament triumph of the year (Solomon won the lucratice Alan King Classic at Las Vegas in the spring) and his most satisfying performance of a summer he is sure he will remember best for a non tennis experience: the 60-hour "EST" self awareness training he took in Miami, while most of his colleagues were playing in Wimbledon.

On the court, Solomon has always epitomized the self-made little man. At 5-foot-6 and 138 pounds, the Silver Spring, Md. native doesn't have the serve, reach, or weight of shot to intimidate opponents.

He wins because he has heart, will, persistence, ground strokes . . . and the nerve to go for the winning shot in a tense situation. His extreme Western forehand and two-fisted backhand ("the gravedigger's stroke") are inelegant, but the beauty of his game is that he has perfected the art of the possible.

"My size has always dictated my style of play. I'm never going to overpower guys," Solomon has stressed since he turned pro six years ago. He accepted that fact early and made himself into a master counter-puncher.

Now, Solomon said "est" has helped him to apply the same pragmatic approach to the rest of his life. To deal with the available world.

"Est" is latin for "It is," and the main principle is that what is, is. You can make it the source of happiness or unhappiness," he said. "It makes you realize that you are the cause of everything that happens in your life, and not the victim. If things aggravate you, it is only because you let them. If a chip on your shoulder is weighting you down, it's because you choose to carry it.

"Obviously the world as we know it doesn't work. There are murders, wars, 15 million people starving every year. The world can only work if every 100-watt light bulb puts out 100 watts, and if you put out your 100 watts every day, you've done as much as you can to make it right."