There were no erupting clay volcanoes, no salt maps, no white rats in cardboard mazes at the 41st annual Westinghouse Science Talent Search finals at the National Academy of Sciences this weekend. None of the magic tricks that pass for science in the school gym. This was serious stuff, young minds burning bright, like the hot white glow of magnesium. Hard-core science.

Forty high school students came from across the country to compete for $89,500 in scholarships, exchange ideas with their peers, and explain their research to onlookers. The winners will be announced at tonight's banquet at the Mayflower Hotel.

The Science Talent Search is nicknamed the "Nobel Farm Club" for its track record: Five Nobel prize winners in the past 10 years, and two winners of the Fields Medal, the Nobel's mathematical equivalent, were Westinghouse winners. Seventy percent of the winners have gone on to receive PhDs. Nobel Prize winner Glenn T. Seaborg, who developed the periodic table for transuranic elements, has been on the panel of judges--comprising eight prominent scientists from around the United States--for 20 years.

Finalist Sharon Marcus, 15, from Flushing, N.Y., patiently explained her project to David and Daniel Bernhardt of Takoma Park, 10 and 8 years old, obviously enthralled by her squirming, multicolored tobacco hornworms. "When kids are interested in science, they usually head straight for the insects, so I have a bigger audience than most," said Marcus, who studied proteolysis, a process of decomposition in insect developmental stages.

"High school labs are in a pitiful state; you can't do anything at all sophisticated," said the poised and articulate Marcus, who did her research at St. John's University. She also plays piano and clarinet, edits her school newspaper and enjoys reading. "I love novels. I read science texts, too, but they don't have that zing.

"One of the people in the labs told me, 'You have to have courage to be a scientist,' " Marcus said. "First, I thought, I can understand people working with radiation being scared, but a lot of scientists are scared. Some change their results, doubt themselves or won't emphasize something important. Dr. Seaborg was revolutionary; he revolutionized the periodic table. He had a lot of courage. Those are the people who usually get into trouble. Like Prometheus up there," Marcus said, gesturing to a large mural above her. "He brought down the fire, and where would we be without that?"

"Don't ask me anything about my project or you'll be 40 when I'm through," joked Theron Stanford, 17, of San Marino, Calif., whose involved paper on advanced number theory was titled, deceptively simply, "Restricted Divisors."

"I had a question about unitary divisors that had never been answered," said Stanford, who has been accepted at Cal Tech. "I love pure mathematics--there's a difference between theoretical and applied math. You never know when the gap between them will jump again. Mathematicians invent things for the beauty of it. A painter doesn't always want to prove something with his painting. Mathematicians think of themselves as the artists of the scientists."

Stanford said he enjoyed the meeting of the minds the science fair afforded. "It's exciting being with 39 other people really interested in science. We'll say, 'Let's go 10 minutes without talking science'--and we can't do it! Or we'll tell some really deep scientific jokes. People don't usually laugh when I tell them at home," said Stanford.

Jonathan Taylor, 17, of Bayside, N.Y., tested the effects of two antibiotics on diseased silkworms. His mother had raised silkworms as a child in Israel. "I've defoliated all the mulberry trees within a 10-mile radius of my home to feed them, though," Taylor said with a laugh.

Like many of the other finalists, Taylor found it necessary to use university facilities to conduct his research, and he's apprehensive about the future of science study in the face of the government scalpel.

"Most people don't appreciate what the impact of Reagan's budget cuts will be," said Taylor. "Fewer high school students will be exposed to science because these National Science Foundation NSF programs are being cut totally from the budget. And just think, if they just didn't build one bomb, they could support all the NSFs."