Saturday afternoon at the Olney Public Library. The place is humming with children--and virtue.

Kids are hard at work typing term papers. Other kids are studying textbooks. Still others are mining the Internet for sports trivia, movie information, puzzles.

But the previous Saturday hadn't been nearly so placid. On that day, according to a father who watched it happen, a man sat at a very public computer terminal in the same library, dialed up pornography on the World Wide Web and began viewing it.

His terminal was one of six that sit in the middle of the library's "showroom floor." The other five were occupied at the time by children, including my reader's 13-year-old daughter. She was working on a paper "about saints, of all things," the father said.

The girl did not notice what the porn-viewer was doing, and my reader said nothing to her, the porn-viewer or the library staff. The porn-viewer did not converse with any of the nearby children, try to touch them or try to show them any pornography.

But he obviously knew that he was doing something that might raise hackles. He printed out "a whole bunch of stuff" on a common printer where any child might have seen "his" sheets, the father said. The printer jammed. A library employee came over to see if she could help.

The man hunched over the sheets that were already in the trough. In a brusque tone of voice, he said no, no, he'd take care of the jam. "It was obvious he was trying to hide what he had printed," the father said.

The father is torn about the incident, because he works as a writer and researcher and believes in the freedom to read whatever one likes in a public library. But since I am the father of teenagers myself, he called to see what I thought about the Olney incident.

First, we climbed the slipperiest slope of all. What was the Olney porn fan actually looking at? After all, one man's porn can be another's master's thesis. Just ask the Supreme Court how easy this one is to sort out.

The father said he hadn't caught more than a couple of fleeting glances. But he assured me that the material was "highly sexual."

Second, a tip of the cap to the Montgomery County library system. It does not seek to be a cop or a censor in cases like this. Here's the system's policy, as explained by Kay Ecelbarger, chief of collection development:

"Pornography is subjective. We do not sequester material, because what shocks one person may not shock another. We prefer to leave that judgment up to the individual and not let the government make that for them."

The system does keep sexually oriented magazines like Playboy behind a counter, however. Adults have to ask for such material. If children ask, they'll be turned down.

As for sexually oriented online material, Kay said there have been a few complaints about inappropriate searching by adults. If someone is causing a disturbance through a sexually oriented search, staff are instructed to suggest that the searcher think about what he or she is doing, and where. The staff would be careful to emphasize that the viewer has the right to keep viewing, Kay said.

In its children's section, the Olney library has two Internet-ready computers where adults are not welcome, Kay pointed out. Obviously, this would protect a child against sitting shoulder to shoulder with a porn-viewing adult.

Of course, children could find pornography themselves on these computers, because they don't have filters. However, the children's section computers are equipped with bookmarks and search engines that strongly steer children toward more appropriate educational sites, Kay said.

It feels unsatisfying to suggest that a father shepherd his 13-year-old into the children's section so she can avoid porn while doing a paper on saints. The "victim" has to hide in a corner of the library, while the porn-viewing "victimizer" gets the run of the room.

But in the never-ending battle between freedom and excess, there's no such thing as perfection.

CHILDREN'S HOSPITAL

Has your social club or religious group passed the hat for Children's Hospital yet?

Each year during our Children's fund-raising campaign, my mail bulges with gifts from such groups, and why not? It's a neat way to make holiday spirits billow and our bottom line flourish. Cherry on top: Your group gets a bold-faced acknowledgment right here in Bob Levey's Washington.

Don't be embarrassed if your group can collect "only" a few dollars. No gift to this campaign is too small. We're deeply grateful for them all--and for all who work so hard to make them happen.

Our goal by Jan. 21: $650,000.

In hand as of Dec. 10: $98,611.32.

TO CONTRIBUTE TO THE CAMPAIGN:

Make a check or money order payable to Children's Hospital and mail it to Bob Levey, The Washington Post, Washington, D.C. 20071.

BY VISA OR MASTERCARD:

Call Post-Haste at 202-334-9000 on a touch-tone phone. Then punch in K-I-D-S, or 5437, and follow instructions.