Whale is a general name for the extensive and varied order of marine mammals termed in science Cetacea. Their origin is obscure, but it is certain that their very ancient ancestors were land animals, evidence of which is afforded by their anatomy, especially in embryonic and very young specimens. Here are classified not only the great true whales but their smaller relatives, the sportive dolphins and porpoises, the grampuses or blackfish, the white whales often seen in the lower St. Lawrence River, the killers, and such out-of-the-way forms as the narwhal, from whose snout projects a long twisted "tusk," which is a strangely overgrown incisor tooth. In all these animals the shape is fishlike, as is required by the fishlike habits; the skin is smooth and usually blackish, or black with white markings; the forelimbs have become paddles and the tail a pair of horizontal flukes. As they are mammals with lungs and breathe air, whales must come to the surface frequently for that purpose. At the instant they emerge the pent-up air is expelled from the lungs through the nostrils at the top of the nose. In the case of the larger species this big discharge of moist breath condenses in the cold air into a visible vapor, often mixed with sea spray, which is called a "blowing"; but no water is expelled from the mouth, with which the "blowholes" have no connection. The smaller kinds of cetaceans, of which the variety is immense, are in the main fish-eaters, but the killer seizes and devours porpoises and seals also, and a band of them may unite to worry a big cachalot to death. Most species go about in small bands, or "schools."

The great whales are of two distinct families: (1) baleen whales, and (2) toothed whales. The first take their name from the blade-shaped plates of horny material (whalebone) hanging, to the number of two or three hundred, from the roof of the mouth, each central blade eight or ten feet long in ordinary cases. These "right" (i. e., proper) whales, as they are called by the men who hunt for and harpoon them, are huge creatures often fifty to seventy-five feet long, ranging all northern oceans, even amid arctic ice; yet, despite their bulk, they feed exclusively on the small crustaceans and other minute creatures of the plankton swept into the mouth by the million as the whale rushes along the surface, the water scooped up escaping from the sides of the mouth, and the food being caught by the fringes of baleen and swallowed like a continuous meal. In addition to the whalebone obtained from these whales the hunters cut away and save the thick layer of fat (blubber) under the skin for the sake of the oil it yields. The beeflike flesh of the muscles is good meat. This kind of whale is becoming very scarce.

The toothed whales consist of the single species called sperm whale, or "cachalot," which is of gigantic size, a lesser cousin ("kogia"), and an inferior genus, the beaked whales of the Antarctic. All are more common in the tropics and South Pacific than elsewhere. The great sperm whale differs in form from a "right" one mainly in having a huge, flattopped, almost square-fronted head, beneath which is hinged a somewhat shorter underjaw. The cavernous mouth is armed with strong, pointed teeth, and these whales prey on fish and especially on cuttlefish. They can swallow whole nothing larger than a salmon, but can bite larger prey into manageable pieces, and have more than once seized and crushed a boat in their jaws. The cachalot attacks the giant squid whenever it meets one and the marks of the squid's winding arms and cruel suckers are often seen on the hides of whales as scars of some struggle between these Titans of the deep. The value to mankind of the sperm whale lies in the liquid fat and the valuable substance, spermaceti, that fill a vast cavity in the top of its skull, a single whale yielding several barrels of it, from which the commercial "spermaceti" and a fine oil are extracted. In their intestines are frequently found lumps of the secretion known as "ambergris," used as a base for perfumes, the price of which is so high in the market that a few pounds will cover the expenses of a ship's voyage. Ambergris is also found floating in the open sea or cast up on shore, and for a long time its origin was unknown.