TEN-YEAR-OLD Kristina Booth demonstrates how to measure time with her homemade ``water clock.'' Tara Cromwell shows off the ``sand clock'' she created using plastic jugs and tape. And Liz Kidd, another classmate in this after-school program, sends a small wooden ball down a paper chute as she experiments with her ``rolling-ball clock.''
For these girls taking part in a unique education program administered by the Lynn, Mass., chapter of Girls Incorporated, a nationwide girls' advocacy group, the fun part is not just in building science experiments. It is writing letters to real scientists from neat places like California and Hawaii about their projects.
In the program, called Science By Mail, young people get hands-on experience by putting together science experiments from kits sent through the mail. Individuals or groups of youngsters are assigned to volunteer scientists from all over the country who act as mentors and instructors to the children.
``They tell us about a lot of stuff,'' says Tara. ``You feel special because someone is writing to you.''
Created by the Boston Museum of Science in 1988, Science by Mail is designed for kids in grades 4 through 9. Participants include home schoolers, classrooms, families, and youth groups.
The program is offered through 15 chapters in the United States and one in Canada.
A chief aim is to reach out to youngsters traditionally under- served by science education, such as girls and minorities. Currently, 50 percent of the program's participants are girls and 18 percent are minorities. Program officials hope to increase those percentages even higher.
``A lot of times [girls] don't have the opportunity to take things apart and build things like you would naturally expect from a young male growing up,'' says Sue Marvit, who administers Science by Mail for Girls Incorporated of Lynn.
``If women don't have some grasp of science and technology, they are going to be extremely limited in an information society,'' she says.
Organizers say the program is meant more to stimulate interest in science and encourage diversity among students than to promote competition.
Last year, a total of 25,000 students participated in the program along with 2,000 scientists from universities, institutions, and corporate laboratories. Teachers, youth-group leaders, or parents actually administer the program on site.
The role of the scientists is to offer tips, encouragement, and advice to the students. Occasionally, scientists will make personal visits to students at schools, or students will visit scientists at their laboratories.
Virginia Wooten, an assistant professor at the Massachusetts College of Pharmacy and Allied Health Sciences in Boston, has been a volunteer scientist pen pal since 1988. Over the years, she has kept up correspondence with one or two youngsters beyond the program.
``I enjoy doing it,'' she says. ``I have a group now that I will probably keep up correspondence with. They will tell you, `I did this,' and I will just comment and say, `Have you tried so and so?' ''
During the program, children receive three science kits, each with a different theme. The kits include an instructional guide, four to six experiments, materials needed to perform the experiments, and a special journal for youngsters to use when writing to their scientist pen pals.
Themes for science kits vary and include topics like sound, time, and weather. Some of the more offbeat themes include the science of ice cream, the making of movie special effects, and the issue of waste management in space.
Each packet also contains a major experiment called the ``big challenge.'' Youngsters complete and send these final projects in the form of drawings, video tapes, models, reports, or photographs to their scientist pen pals.
The program is not without problems. The lag time in letter response from scientists has been an issue for Ms. Marvit, who administers a shortened 10-week session of the program.
In the future, Marvit will encourage youngsters to use E-mail and the fax machine for correspondence. In general, most scientists are good about letter writing, program organizers say.
Alice Cronin-Golomb, a Boston University assistant professor of psychology, is a volunteer pen pal along with her husband, Mark, a Tufts University professor of electrical engineering.
When writing to students, the two try to include personal information about themselves as well as a photograph.
``We send detailed letters of introduction. We tell them things like we have two cats and I play the saxophone and we both like to garden,'' says Ms. Cronin-Golomb. ``We tell them a lot of personal stuff so they feel like we are real people.''