A conservation project at the University of Virginia has unearthed an elaborate chemical laboratory within the walls of the university Rotunda dating to the time of Thomas Jefferson.

A sophisticated chemical hearth for lab experiments, complete with multiple heat sources and vents providing ways to control the heat, offers a glimpse of how science was taught to students during Jefferson's time, university officials say.

Part of an early science classroom, the hearth had been sealed away within the Rotunda walls in the 1850s when it was no longer in use.

That protected it from a disastrous 1895 fire that destroyed the majority of the building interior, experts say.

During renovations made necessary by crumbling support columns and water leads, workers were examining cavities within the walls when they discovered the chemistry hearth.

"It was a surprise, a very exciting one for us," says Brian Hogg, senior historic preservation planner in the Office of the Architect for the University.

The university's Academical Village, site of the Rotunda, has been names a World Heritage Site by UNESCO.

Teaching of chemistry took place on the bottom floor of the Rotunda, with classes led by John Emmet, the university's first professor of natural history.

Emmet collaborated with Thomas Jefferson to equip the space used for teaching.

In a letter to the university's Board of Visitors, Jefferson specified that the chemistry room be on the ground floor of the Rotunda.

"For the Professor of Chemistry, such experiments as require the use of furnaces, cannot be exhibited in his ordinary lecturing room," Jefferson wrote.

In 1824 the board approved Jefferson's proposal.

The hearth could well be America's oldest surviving artifact of chemistry education, researchers say.

"It's exciting," says Jody Lahendro, a preservation architect for the university.

Reading letters between Jefferson and Emmet, emphasizing the then progressive idea of students being active participants in experiments rather than just observing them, "really brought me back to that time," he says.

"It really is the beginning of the teaching of science," as one of the defining activities of a university rather than religion studies, he notes.

When the renovations to the Rotunda are completed the hearth, along with historical information on the site and the people involved, will be on permanent display for students and visitors, the university says.

A barrier will prevent people from entering the alcove containing the hearth, but the complete hearth will be visible to visitors, it says.