The central mountainous region of Cuba is situated in the Province of Santa Clara. This system consists of four groups having a general direction toward north and south and at [Illustration: THE FAMOUS PALMS OF CAMAGUEY.] points reaching both coasts. In the area between Cienfuegos, Trinidad and Sancti Spiritus is an extensive cluster of rounded hills, dominated by Potrerillo, nearly three thousand feet high, and interspersed with the most beautiful and fertile valleys. The Cordillera de los Organos, or Organ Mountains, run almost along the middle line of the Province of Pinar del Rio, paralleling the northern coast. The range commences about twenty miles to the west of the boundary of Habana Province and extends to the estuary of the Colorado, thus traversing three-fourths of Pinar del Rio. The greater part of the Province of Camaguey is free from hills. The principal elevations are found in the north-eastern portion, where the Sierra de Cubitas is situated. Aside from the mountains and hills described, the general surface of Cuba is a low, gently undulating plain. The elevations of some of the principal interior cities are as follows: Pinar del Rio, one hundred and three feet above sea level; Cuevitas, ninety-eight feet; Camaguey, three hundred and twenty-four feet; Santa Clara, three hundred and forty feet. Except in the southeast corner of Oriente, the streams of Cuba all follow a normal course to the coast. Owing to the shape of the Island, therefore, none of them has any considerable length or volume, nor are any navigable with the exception of the Cauto, which permits of the passage of light draft boats to a distance of fifty miles from its mouth. Cuba is noted for its spacious land-locked harbors. Their extraordinary lake-like formation has been the subject of many more or less fanciful explanations. The following statement of Dr. C. W. Hayes, of the U. S. Geological Survey, seems to fully account for the phenomenon: