The perpetuation of the Merino sheep in all its purity, amid the convulsions which changed the entire political framework of Spain and destroyed every other national improvement, strikingly illustrates the primary determining power of blood or breeding, as well as the agency of soil and climate--possibly too much underrated in modern times. These Spanish sheep are divided into two classes: the _stationary_, or those that remain during the whole of the year on a certain farm, or in a certain district, there being a sufficient provision for them in winter and in summer; and the _migratory_, or those which wander some hundreds of miles twice in the year, in quest of pasturage. The principal breed of stationary sheep consists of true Merinos; but the breeds most sought for, and with which so many countries have been enriched, are the Merinos of the migratory description, which pass the summer in the mountains of the north, and the winter on the plains toward the south of Spain. The first impression made by the Merino sheep on one unacquainted with its value would be unfavorable. The wool lying closer and thicker over the body than in most other breeds, and being abundant in yolk--or a peculiar secretion from the glands of the skin, which nourishes the wool and causes it to mat closely together--is covered with a dirty crust, often full of cracks. The legs are long, yet small in the bone; the breast and the back are narrow, and the sides somewhat flat; the fore-shoulders and bosoms are heavy, and too much of their weight is carried on the coarser parts. The horns of the male are comparatively large, curved, and with more or less of a spiral form; the head is large, but the forehead rather low. A few of the females are horned; but, generally speaking, they are without horns. Both male and female have a peculiar coarse and unsightly growth of hair on the forehead and cheeks, which the careful shepherd cuts away before the shearing-time; the other part of the face has a pleasing and characteristic velvet appearance. Under the throat there is a singular looseness of skin, which gives them a remarkable appearance of throatiness, or hollowness in the neck. The pile or hair, when pressed upon, is hard and unyielding, owing to the thickness into which it grows on the pelf, and the abundance of the yolk, retaining all the dirt and gravel which falls upon it; but, upon examination, the fibre exceeds, in fineness and in the number of serrations and curves, that which any other sheep in the world produces. The average weight of the fleece in Spain is eight pounds from the ram, and five from the ewe. The staple differs in length in different provinces. When fatted, these sheep will weigh from twelve to sixteen pounds per quarter.