I have just been named registration committee chairman for the St. Mary's County science fair, to be held March 8 and 9.

Students in grades six to 12 from throughout St. Mary's will soon be sending me their entry forms, looking to me, as to some omniscient demigod, for sanction and reassurance.

"Data Plotting on the Apple IIe." "Bacteria in the Wind." "Hydrostatic Durability." "Does Music Affect an Earthworm?"

Wise guardian of the universe's eternal categories, I will make sure that each young scientist has entered his or her project in the appropriate subject area.

And I am empowered to split up categories as well, expanding creation, as it were, in the interest of easier judging and more prizes.

I do not plan to tell the students and their parents that, by temperament and aptitude, I am more fit to hunt snarks than to analyze quarks.

But although I speak the sciences with a heavy accent, I can converse well enough to grasp the gist of the average science fair proposal.

"Friction in a Force System: My project is pulling pieces of wood across different surfaces."

"Modern Electronics: To design a circuit . . .that will incorporate electromagnetism, light refraction, solar power and the simplicities of modern man."

"Asphalt: My project explains how asphalt is blended with other materials to serve the public."

"The Brain: How it functions, how it helps us, and the parts."

Don't let the awkwardness of the English mislead you. Writing, after all, is a national problem. Moreover, some of these kids, through no fault of their own, are the children of engineers, that skillful breed which tends to be able to assemble anything except a sentence.

I am poking fun with fondness, of course. For the presence of so many high-tech professionals in our community is one thing that gives the St. Mary's County science and engineering fair its peculiar and complex resonance.

Military technology dominates economic life here, by virtue of two naval enginering bases and their attendant circle of defense contractors. The science fair, too, depends upon the Navy, but for more complicated reasons.

Because St. Mary's has a strong parochial school system -- a product, no doubt, of the county's Catholic roots -- the science fair is run not by the local Board of Education but by an independent volunteer board including parents, defense professionals, St. Mary's College professors and teachers from private as well as public schools.

This almost unheard-of arrangement relies upon, and in turn fosters, a community spirit that is impressive to behold. But it also means that the fair's survival (and it is now in its 25th year) depends on private donations: of time, facilities, and equipment, no less than money.

This is where the Navy is indispensable. The local bases consistently provide the fair with a good portion of its funding and many of its board members and judges. In addition, both the Navy's experts and the college's scientists often give advice to students attempting particularly difficult experiments.

But, like the county itself, the fair has a life and flavor of its own, independent of the Navy. This I gathered in the course of a long chat with John Devoe, a Xavierian brother who teaches at Mother Catherine Spalding School in Helen, Md., and is one of the fair's original organizers and the unofficial curator of its memorabilia.

Devoe smokes a sweet-smelling pipe, sports a gray mustache and comfortable-looking flannel shirt, and doesn't appear to mind the jagged hole in one lens of his eyeglasses -- all of which give him a rather distracted and secular academic air.

Browsing through the thick looseleaf folders that serve as the annals of the fair, Devoe pointed out that, despite the Navy's involvement, the fair never has been inundated with exhibits on aviation or other fields of local military expertise. Instead, the students seem to have been drawn by more traditional themes: botany and solar energy, heredity and blood circulation, robots, model dams, and volcanoes.

The St. Mary's scene has evidenced itself in the form of projects on crabs, oysters, water pollution and farming (usually tobacco, though there was once an intriguing exhibit called "Is St. Mary's County a Banana Belt?").

The most striking trend in science fair history, however, has been the dramatic falloff in participation by older students.

In 1965, the fifth year of the St. Mary's fair, 107 senior high school students entered exhibits, and only a limit for each school prevented more from participating.

By 1971, the number of entries in the senior high division had fallen to seven. In 1974, just two entered. The fair almost disbanded in 1977.

The decade from the mid-1960s to the mid-1970s brought vast social changes, certainly. Since then it has become fashionable again to look to science for salvation. We shall perfect the individual through genetic enginering, salvage our economy with computers, and protect ourselves from the aliens with "Star Wars" technology.

But, curiously, senior high students are not clamoring to return to the science fair. Last year there were only 10. And the level of sophistication doesn't seem to rival the days when James Boyd, now an internist in Leonardtown, entered "Lungless Frogs" and George Sparling (now a local lawyer) discussed "the curvature of quadratic surfaces."

My theory is that the younger students remain faithful to the science fair because they still have the inclination to play and the freedom to lose themselves in their curiosity.

Older students today have to contend with more complex pressures and responsibilities. They learn the most central lesson of adulthood: It is more important to obey the rules than to wander after the whims of the enquiring mind.

Devoe, on the other hand, points out that a school and its teachers can make a difference. His school has its own science fair every February, and each sixth-, seventh- and eighth-grader is required to prepare a project.

The school buys equipment and lets the students take it home to work on their exhibits.

Devoe always is on call for crises: water fleas that won't breed, caterpillars that die, amoebae that refuse to reveal their whereabouts under the microscope.

Outside judges come in to talk with the exhibitors and award prizes.

The experience tends to cultivate poise and a new sense of possibilities. This brings Devoe a special satisfaction, one that echoes every September, when some youngster comes to him and says earnestly, "Brother, I want a really hard project this year."