The dogs that are selected for this purpose are those the conformation of whose face and head gives ample room for the development of the olfactory apparatus, and these are the different species of hounds; but a systematic education, and too often a great deal of unnecessary cruelty, is resorted to, in order to make them perfect in their work. The distinction between the scent of the fox and that of the hare is soon learned by the respective packs; and, when it is considered that the hunted hare is perspiring at every pore, and her strength being almost exhausted, she is straining every limb to escape from her pursuers, the increasing quantity of vapour which exudes from her will prevent every other newly started animal from being mistaken for her. It has been well observed that when the atmosphere is loaded with moisture, and rain is at hand, the gas is speedily dissolved and mingles with the surrounding air. A storm dissipates it at once, while the cessation of the rain is preceded by the return and increased power of scent. A cold, dry easterly wind condenses and absorbs it, and this is even more speedily and irretrievably done by superabundant moisture. On fallows and beaten roads the scent rarely lies well, for there is nothing to detain it, and it is swept away in a moment; while over a luxuriant pasture, or by the hedge-row, or on the coppice, it lingers, clinging to the grass or the bushes. In a sunshiny day the scent is seldom strong; for too much of it is evaporated by the heat. The most favourable period is a soft southerly wind without rain, the scent being of the same temperature and gravity with the atmosphere. Although it spreads over the level, it rises not far above the ground, and, being 'breast high', enables the hound, keeping his muzzle in the midst of it, to run at his greatest speed. The different manners or attitudes in which the dog runs afford pleasing and satisfactory illustrations of the nature of the scent. Sometimes they will be seen galloping with their noses in the air, as if their game had flown away, and, an hour or two afterwards, every one of them will have his muzzle on the ground. The specific gravity of the atmosphere has changed, and the scent has risen of fallen in proportion. A westerly wind stands next to a southerly one, for a hunting morning. This is all simple enough, and needs not the mystification with which it has been surrounded. A valuable account of this may be found in Johnson's Shooting Companion, a work that is justly and highly approved.