A sundial that tells the exact time of day and a study of life in the Black Swamp in South Carolina were two science projects that won top prizes in local fairs.

Clay Stern, a 17-year-old senior at Paint Branch High School in Burtonsville, was one of the two students who won grants to attend the national science competition in Anaheim, Calif. Stern spent several months studying and photographing snakes in the Black Swamp.

The other top winner in Montgomery County was Duncan Perry, a sophomore at Whitman High School in Bethesda.Perry's project drew an analogy between electrical voltage fields and fluid fields, such as wind.

Top winners in the Prince George's fair were Stephen A. Lloyd, a 10th grader at Eleanor Roosevelt High School, and Michael Stehpen Briggs, a senior at High Point Senior High School in Beltsville. Both won grants to go to Anaheim, Calif.

Lloyd devised a sundial that uses a prism to refract the sun rays in a given length to determine the exact time of day.

Briggs, who also won the top prize of a $10,000 scholarship in the national Westinghouse Science Talent Search, studied two finite games, or games with solutions, in order to solve or approximate a solution to infinite games, or games with no solutions.