Sheep may be wanted almost exclusively for the fleece, or for the fleece and heavy mutton, or in the neighborhood of markets, for large early lambs. The pastures and winter food, climate, and other conditions, present additional circumstances, which should be well considered before determining on the particular breed, either of cattle or sheep, that will best promote the interest of the farmer. The kind of work for which the horse may be wanted, whether as a roadster, for the saddle, as a heavy team horse, or the horse of all work, must be first decided, before selecting the form or character of the animal. The range of pig excellence is more circumscribed, as it is only necessary to breed such as will yield the greatest amount of valuable carcass, within the shortest time, and with the least expense. PRINCIPLES OF BREEDING. All breeding is founded on the principle, that _like begets like_. This is, however, liable to some exceptions, and is much more generally true when _breeding down_ than when _breeding up_. If two animals (which can never be exactly similar in all respects) are requisite to the perpetuation of the species, it necessarily results, that the progeny must differ in a more or less degree from each parent. With wild animals, and such of the domestic as are allowed to propagate without the interference of art, and whose habits, treatment, and food are nearly similar to their natural condition, the change through successive generations is scarcely perceptible. It is only when we attempt to improve their good qualities, that it is essential carefully to determine, and rigidly to apply, what are adopted as the present scientific principles of breeding. We cannot believe that we have penetrated beyond the mere threshold of this art. Unless, then, we launch into experiments, which are necessarily attended with uncertainty, our duty will be, to take for our guide the most successful practice of modern times, until further discoveries enable us to modify or add to such as are already known and adopted. We may assume, then, as the present rules for this art, 1st. That the animals selected for breed, should unite in themselves all the good qualities we wish to perpetuate in the offspring.