A dirt-encrusted button, some shards of terra cotta and the buried remnants of a mysterious rock circle were fresh treasures unearthed in the Presidio last week by archaeologists probing the ground at El Polin Springs, where soldiers of the Spanish-American War once slaked their thirst.

The scientists' high-tech tools and their sweaty digging - plus siftings from a jury-rigged wire screen - had uncovered new evidence that the meadow could once have held the homes - or perhaps the ranch - of Spanish colonial families that settled just outside El Presidio de San Francisco not long after Spanish soldiers built the fort in 1776.

More excavations in the dry, unshaded meadow - known as Tennessee Hollow and cleaved now by a dead-end asphalt road - could result in many additional clues to the people who lived in the Presidio, the archaeologists say...