More than half of Santa Clara is hilly and broken, although owing to the fertility of the soil this interferes but little with the agricultural development of the Province. The mountains of Santa Clara form the central zone of the great volcanic upheaval that raised Cuba from the depths of the Caribbean. A broad belt or double chain lies between the city of Santa Clara and Sancti Spiritus. Another ridge, just south of the latter city, extends from the Tunas de Zaza railroad to a point east of the Manatee River, near the harbor of Cienfuegos. A second group lies between the valleys of the rivers Arimao and Agabama, names taken from the original appellations given them by the Indians. The highest peak of this central region, called Potrerillo, is located some seven miles north of Trinidad and reaches an altitude of about 3,000 feet. The mountains of this group extend northwest as far as the Manicaragua Valley. A third group, lying southeast of the city of Santa Clara, includes the Sierra del Escambray and the Sierra de Agabama. The average altitude of these latter hills is only about a thousand feet. Another range of hills begins at a point on the north coast of the Province, twenty-five miles east of Sagua la Orande, and runs parallel with the north shore of the Island into the Province of Camaguey, in the western edge of which it disappears in the great level prairies of that region. The highest peaks of this group are the Sierra Morena, west of Sagua la Grande, and the Lomas de Santa Fe, near Camajuani. A little further east they are known as the Lomas de Las Sabanas. With the exception of the northern coast range, the other ranges of Santa Clara have resulted from seismic forces, working apparently at right angles to the main line of upheaval, leaving the tangled mass of hills and valleys characteristic of this great central zone of the Province. What is known as the schistose or pre-cretaceous limestones of Trinidad, are supposed to be the oldest geological formations in the Island of Cuba. From the foot of the Sierra de Morena, near the north coast, a wide, comparatively level plain sweeps across the province to the Caribbean Sea, broken only at a few points by one or two abrupt hills, northeast of Cienfuegos. Lying between the northern chain of mountains and the coast, we find quite a broad area of rich level land washed by the salt water lagoons of the north shore. Again, in the extreme southeast corner of Santa Clara, is found another large tract comprising perhaps a thousand square miles, located between the Zaza and the two Jatabonico rivers that form the boundary between the province and Camaguey.