The herring propels itself through the water by rapidly moving the tail from side to side, the other fins being employed in steadying and probably aiding its movement, and it is this rapid waving of the tail which causes the rippling or pattering sound which announces the presence of a shoal when swimming near the surface. On a calm night their course may be traced by a brilliant phosphorescent light, which illuminates the surface of the water, and is emitted partly from the fish themselves, and partly from the minute marine animals with which the ocean swarms. Sometimes herrings do not approach the surface, and fine healthy shoals are often apt to swim deep; hence fishermen, through their ignorance in trusting too much to appearances, are frequently misled, they being apt to suppose that when they see no gulls or large fishes of prey exhibiting their gluttonous gambols, there are no herrings present, whilst the finest and choicest may be at the moment in millions beneath them; in fact, those which swim near the surface are usually the young, the gorged, and the sickly. Mr Mitchell informs us that several experienced masters of Dutch herring busses assured him that the only appearances they ever sought for were the colour of the sea, which should be a dark green, and its consistence apparently muddy. There is an additional fact worthy of observation, which is, that in clear dry weather the fish keep down at the bottom, and do not ascend until the moon rises. The migration of the herring has been long a disputed point, and from the difficulties to which we have alluded in the commencement of this article, of observing minutely or accurately the movements or nature of fishes, it is likely to remain unsettled much longer. The old and long received opinion has been, that the winter habitation of the herring is under the vast fields of ice which surround the North Pole within the Arctic Circle; that they there deposit their spawn and advance southwards with the opening year, making their appearance off the Zetland islands about the month of April, and coming upon the coasts of Ireland and Scotland in June. Off Thurso they are sometimes taken as early as May, but June, July, and August, are the months in which the fishing is most actively commenced off the west Highlands of Scotland. Off the east coast of Ireland, near Arklow, the fishery used to commence in June, but latterly it has been postponed till October. The fluctuations in the time of commencing the herring fishery at various places, and the fact of a winter fishery being successfully carried on in some parts--as for instance at Killybegs, where they are taken from December till March, and along the whole coast of Ireland south of Galway Bay, where there are sufficient indications that the fishery might be successfully carried on the whole year--have at length caused the hitherto received opinion of their migration from the Arctic Circle to be questioned, and Mr