The Horse has been subjected to the service of Man from the earliest records, indeed it is not known when this beautiful animal was first trained to be his useful servant and companion; he is mentioned, in the Scriptures, as being subjected to the Bit, and in the sculptures brought from the ruins of Nineveh by Layard; the Horse is constantly sculptured, decked in the most gorgeous trappings and driven by reins and a bit, almost in the same manner as in the present day, and these sculptures are among the earliest records of Man's hands. There are several breeds of Horses; the chief are the Arabian (from which stock proceed our race horses), the Flanders or Cart-horse, and the Sheltie or Shetland horse. The Horse is nowhere found in a state of nature, yet many wild Horses graze on the plains of America, but it is known that these are not native, but proceed from those placed there to graze, and which have bred and run wild. The Ass is distinguished from the horse by the tail having short hair on it, except at the extremity, and the mane being short and upright. 7. The CETACEA, or Whale kind, inhabit chiefly the colder latitudes, they are entirely aquatic, but breathe air; the Whale, Narwal, Dolphins, and Porpoises are the chief members. [Illustration: FIG. 65.--WHALE (Balena mysticetus),] In Whales (fig. 65) the anterior extremities are so developed as to form a sort of fin called a "flipper," but in which all the usual bones of an extremity exist; the posterior extremities are modified so as to completely resemble the tail of a fish; they have smooth skins devoid of hair. All these tribes have a considerable thickness of fat or blubber (as it is called) beneath their skin; this protects them from the cold, for most of these creatures live in the very coldest climates, the oily matters acting as a non-conductor; it is for the oil yielded by this blubber that they are chiefly caught. The Cachelot or Sperm-whale (Phyceter macrocephalus) also yields spermaceti, which crystallizes from the oily matter contained in its head, and the Greenland-whale yields baleen or whale-bone, which is a substance forming a sort of sieve in the mouth, through which they draw the sea water and catch all it may contain for food, this consists of all small fish, but principally a small mollusc called the "Clio Borealis," which inhabits the northern seas in great numbers; a whole shoal of these is taken in by the Whale at a draught. The Whale often measures 60 or 70 feet in length, and the Razor-back Whale sometimes 100; a large Whale will yield 20 tuns of oil. The Narwal or Sea Unicorn is from 20 to 30 feet long; it has but one tooth, which is developed to a prodigious length, and projects in front in a straight line like a sort of horn, there are however sometimes two of these, one being always much larger than the other; this horn is 8 or 10 feet long, perfectly straight and twisted, it is used by the animal to break the ice so that it may