Thirst is a compound sensation. There are pain and a desire for that which is known to remove the pain. The two co-exist, but the pain always precedes the desire. The sensation in ordinary circumstances is governed by the wants of the body. Thirst depends not upon a particular state of any one part, but upon a particular state of all parts, to whose welfare fluid is necessary. Water is consumed in almost every living process. Whenever a new supply is wanted, a painful sensation arises which the animal hastens to relieve. The pain does not cease till water has been taken in sufficient quantity to meet the internal demand. If fluid can not be obtained, the sensation, at first only a slight uneasiness, becomes more vivid, and gradually proceeds to intense torture. Except by accident, the thirst never acquires all the intensity of which it is capable. But water is too often withheld till the desire becomes very strong and painful. It is permitted to exist so long that, the thirst can not be allayed at once, and by the ordinary means. It is several minutes, possibly some hours, before all parts of the body can be supplied with that which they have so long and so urgently demanded.

Thirst, therefore, continues for a good while after the stomach and bowels have received sufficient to supply all the system. The horse continues to drink, however, until the pain of thirst is somewhat lost in the pain of distension. Very often he takes so much as to hurt himself. When the horse has water always before him he never does this. But it is still doubtful whether all horses should have water as they please to take it.

Thirst makes a horse refuse his food, and makes him slug gish, I am not sure if it produces any actual debility; yet in many cases it comes to the same thing. If he be unwilling to go, a race may be lost as certainly as if he were unable to go. When the pain of thirst becomes very intense, the horse becomes unmanageable at the sight of water, He will bolt off the road and plunge headlong into a river, clearing every obstacle in his way with astonishing alacrity.

The Kind of Water perferred for horses is that which is soft. Hard water seems to be quite as good after the horse has become accustomed to it. At first it disorders the skin and the bowels a little. The hair stares and the skin is rigid; the bowels are relaxed, and at fast work the horse is apt to purge. In two or three works, often in as many days, he regains his usual appearance, and continues to thrive as well on this hard water, as he previously did on the soft. How far the sudden change may affect his speed or his spirit I do not know. He may be weak; and training grooms generally avoid hard water, in fear of its influence upon the horse's power. It is not likely that the skin and the bowels may be thus disordered without alteration in other parts; but I have not been able to perceive any. Nevertheless a change from soft to hard water ought, if possible, to be avoided on the eve of a great performance. Hunters and racers travel to many strange places; and when immense sums are pending upon their exertions, it is prudent to exclude the operation of every dubious agent.

Possibly water may be carried with the horse, or inquiry may discover similar water in the neighborhood of his destination.

Hard water may be softened a little by boiling it, and the addition of about half on ounce of the carbonate of soda to every pailful of water, renders it softer, but not, so far as I know, more fit for drinking. A change from hard to soft water does not seem to produce any visible effect upon the horse.