The Loudoun Board of Supervisors voted unanimously Monday to place a bond issue on the Nov. 3 ballot that would allow the county to purchase the 370-acre Claude Moore Conservation Education Center to preserve it as open space.

The action by the board marked the first time the county had agreed to borrow money for such a purpose, but some supervisors said it will probably not be the last in fast-growing Loudoun.

The board will decide next week on the amount of the bond issue, which could be as much as $25 million, supervisors said.

Moore, a 95-year-old physician, said he donated his historic farm to the National Wildlife Federation in 1975 with the verbal understanding that the group would preserve the land as a wildlife refuge.

Last year, the federation sold the eastern Loudoun tract to McLean developers Miller and Smith for $8.5 million.

Federation spokesmen said they sold the farm because it duplicated activities at an education center 10 miles away, and that profits from the sale would be used to set up a conservation fund for endangered plant and animal species.

Last month Moore, who attended Monday's meeting, filed suit in Loudoun County Circuit Court to block the developer's proposal to build 1,146 houses, condominiums and apartments on the land, which is near Sterling on Rte. 637.

In the suit, Moore charged fraud and deceit by the federation.

Monday's public hearing on the issue also marked another first: According to board Chairman Betty W. Tatum, whose Guilford District includes the Moore tract, the crowd of 125 residents, which was unanimously in support of the purchase, included an equal number from both ends of the county.

Historically, residents from the more highly developed eastern end and Loudouners from the county's mostly rural western half are sharply divided on most issues.

"I'm elated about the board's decision and about the unity this county showed tonight," Tatum said later.

"But we had the choir members here -- people who already support the preservation of open space. The hard work is still ahead of us."

An appraiser hired by the county informed the board Monday that the Moore property is worth $13 million.

Julia Taylor Cannon, the developer's attorney, told the board that the land is worth closer to $30 million.

Cannon also reminded the board that the developer's proposal, which is being studied by the planning staff, includes the offer of a 50-acre park, a 3-acre school site, and 16 acres for ball fields.

But speaker after speaker noted that open space is rare in eastern Loudoun.

If the Moore property is not preserved, they said, that end of Loudoun would lose the opportunity to have such a preserve, which is home to 200 species of birds and 30 mammal species.

When the board presented Moore with a framed depiction of the county seal, in appreciation of his original donation, the crowd applauded enthusiastically.

Said one speaker, quoting the political satirist Will Rogers: "They ain't making any more land."

CAPTION: Dr. Claude Moore, 95, sued after the National Wildlife Federation sold his donated 370-acre farm to developers.