Later a fortified line was constructed extending across the peninsula between the bay and the San Sebastian River, “about a cannon shot north of the fort.” It was called the _Hornwork_ because a portion of it resembled in shape the horn of a steer. It consisted of a wide ditch and embankment of earth and sod, at one time further strengthened by a stockade of logs, and a fort at its eastern extremity. Another defense line extended north and south along Maria Sanchez Creek in the vicinity of present Cordova Street, marking the western boundary of the original settlement. Other defense works protected it on the south. The lines were strengthened at intervals by redoubts and angular projections, in some of which cannon were mounted. Sentinels manned the defense lines day and night, once each hour passing the _Alerto_. When escaped Negro slaves began to find refuge in St. Augustine, a small fort was built for their protection two miles north of the town. It was called Fort Mosa, or the Negro Fort, and served as an anchor for another defense line running east and west. Practically no evidence of this fort and defense work has survived. _Palmer’s Raid_ The Yamassee Indians of Carolina, once allied with the English, turned against them and in 1715 were decisively defeated. The Spaniards in Florida were accused of fomenting this revolt. A remnant of the tribe took refuge in the St. Augustine area where, according to English reports, they were welcomed by the ringing of bells. For some reason the Yamassees were banished for a time south of the city. They were later recalled, given weapons, and encouraged to make raids on the Carolina border plantations, bringing back bloody scalps and an occasional prisoner. [Illustration: _A gun emplacement in the defense lines. The platform sloped forward to absorb the gun’s recoil._] To put an end to these raids a Colonel Palmer swept south from Carolina in 1728 with a small force of militia and Indians. They surprised and butchered some of the Yamassees in their villages north of St. Augustine, but could not penetrate its now strong outer defense line. After destroying everything of value outside the city, and seizing many Spanish-owned cattle, Palmer returned to Carolina. Following his departure the Spanish governor ordered the destruction of the mission chapel of _Nombre de Dios_, which had afforded the English cover in their attack.