by means of lungs, fishes are furnished with gills. These gills consist of a series of thin fleshy leaves, minutely interspersed with blood-vessels; and by inhaling and passing the water continually through these, the particles of air contained in the water are absorbed and carried into the blood. Such is the extent of surface presented by these gills to the water, that Dr Monro calculated the whole gills of a large skate to be equal in extent to the whole external surface of the human body. These gills are very sensitive, and the least injury done to them gives great pain to the fish. When it is an object to preserve fish as long as possible in a fresh state, the method the fishermen adopt is to cut these gills, and let the fish bleed profusely, after which it is less apt to become putrid.

Another singular circumstance in the construction of fishes is the air-bag with which they are furnished. This consists of a long thin membranous bag, running along the belly in contact with the back-bone, and which is filled with air. Whenever the fish wishes to descend in the water, it compresses this bag into a small compass, and of course diminishes its specific weight; and when, on the contrary, it mounts to the surface of the

water, it expands this bag, thereby rendering the body greatly more buoyant. Fish, as is well known, propagate their species by means of spawn, or a series of minute eggs, and the prolific powers of some fish is quite astonishing. A cod-fish in one season will produce about three and a half millions of young, the flounder one million three hundred thousand, the mackerel upwards of five thousand, and the herring from three to four thousand.

In general, fish before spawning leave the deep water, and approach the shallows, where they deposit their roe, that the young may be vivified by the genial warmth of the sun. Some species leave the sea altogether, and repair to the fresh-water rivers for this purpose; and the most remarkable of these is the salmon.

There are two species which generally go under the common name of salmon,-the sea-trout, and salmon properly so called. The sea-trout is generally of less size than the salmon, has a large head, and is not quite so round and plump in the body. The fins, too, are different, and the spots on the body are larger, and contain a greater proportion of the black and brown colour than those of the

salmon. It is also a more voracious and greedy fish than the other.

At a certain period of the year, which varies somewhat as to time in almost every different river, the salmon forsake the sea, which is their ordinary haunt, and enter the fresh water. It is remarkable, that they always make choice of the particular river where they have themselves been pro'duced. This fact has been ascertained beyond a

doubt, for there is often a marked difference in the appearance of salmon caught in one river from those of another; and it is well known that the other kinds of trout of rivers differ remarkably according to their locality. Some have supposed that the peculiar smell of the waters may guide the instinct of the salmon in this selection, and the idea is not unlikely; for the waters of rivers differ materially, sometimes both in colour and odour, according to the strata of soil which they pass through.

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Up, then, the current of the river the salmon pushes its way with almost unremitting effort. No obstacles are so great but what it surmounts, and no toil so discouraging but what it overcomes. hausted by fatigue, it occasionally passes the sultry noon among the reeds and sedges, but at night it renews its journey, and day after day it bears up against currents, and eddies, and every opposing obstacle.

See where the whole mass of water of the majestic river comes boiling over that steep and tremendous precipice. One cleft of the grey mountain seems to have been forcibly rent asunder to allow the current an outlet, and huge fragments of

rocks stand out in the middle, and lie piled up in rude shapes at the bottom and on either side, over and amidst which the waters foam, and boil, and roar in deafening commotion! Here, one would think, was a barrier impassable; but mark that sudden spring of the salmon, its wheeling motion up the torrent, and its glittering scales shining in the sunbeam. It has failed in gaining the top, and down again it is carried with the current; not to be repulsed, however, it again collects its strength,—it seems either to bend itself round and spring up like a willow-wand which has been bent, or the muscular force of its tail aids it in taking the leap. This time it is more successful, and with one spring, like an arrow from a bow, it fairly gains the top of the waterfall, and pursues its upward course; another and another from below succeeds, and thus hundreds follow in succession. Such a scene we have witnessed amid the wild scenery of Kilmorack, where the story is prevalent, that a Highland chief used to place a fire, with a kettle of water, immediately by the side of the torrent, and whenever an unfortunate salmon leaped out of its course, it fell into the vessel, and was boiled alive!

Having thus ascended to the shallow creeks and