Judging from the mixture of wool and hair in the coat of most animals, and the relative situation of these materials, it is not improbable that such was the character of the fleece of the primitive sheep. It has, indeed, been asserted that the primitive sheep was entirely covered with hair; but this is, doubtless, incorrect. There exists, at the present day, varieties of the sheep occupying extensive districts, that are clothed outwardly with hair of different degrees of fineness and sleekness; and underneath the external coat is a softer, shorter, and closer one, that answers to the description of fur--according to most travellers--but which really possesses all the characteristics of wool. It is, therefore, highly improbable that the sheep--which has now become, by cultivation, the wool-bearing animal in a pre-eminent degree--should, in any country, at any time, have ever been entirely destitute of wool. Sheep of almost every variety have at times been in the gardens of the London (Eng.) Zoölogical Society; but there has not been one on which a portion of crisped wool, although exceedingly small, has not been discovered beneath the hair. In all the regions over which the patriarchs wandered, and extending northward through the greater part of Europe and Asia, the sheep is externally covered with hair; but underneath is a fine, short, downy wool, from which the hair is easily separated. This is the case with the sheep at the Cape of Good Hope, and also in South America. The change from hair to wool, though much influenced by temperature, has been chiefly effected by cultivation. Wherever hairy sheep are now found the management of the animal is in a most disgraceful state; and among the cultivated sheep the remains of this ancient hairy covering only exists, to any great extent, among those that are comparatively neglected or abandoned. The filament of the wool has scarcely pushed itself through the pore of the skin, when it has to penetrate through another and singular substance, which, from its adhesiveness and color, is called _the yolk_. This is found in greatest quantity about the breast and shoulders--the very parts that produce the best, and healthiest, and most abundant wool--and in proportion as it extends, in any considerable degree, over other parts, the wool is then improved. It differs in quantity in different breeds. It is very abundant on the Merinos; it is sufficiently plentiful on most of the southern breeds, either to assist in the production of the wool, or to defend the sheep from the inclemency of the weather; but in the northern districts, where the cold is more intense and the yolk of wool is deficient, a substitute for it is sometimes sought by smearing the sheep with a mixture of tar, oil, or butter. Where there is a deficiency of yolk, the fibre of the wool is dry, harsh, and weak, and the whole fleece becomes thin and hairy; where the natural quantity of it is found, the wool is soft, oily, plentiful and strong.