(edit. 2d, 8vo. 1799, price 7s.), says, with equal truth and precision, that "in the earlier stages of exercise, before profuse perspiration has dissipated the heat, and fatigue debilitated the living power, nothing is more safe, according to my experience, than the cold bath. This is so true, that I have, for some years, constantly directed infirm persons to use such a degree of exercise, before immersion, as may produce some increased action of the vascular system, with some increase of heat, and thus secure a force of re-action under the shock, which otherwise might not always take place. But, though it be perfectly safe to go into the cold bath in the earlier stages of exercise, nothing is more dangerous than this practice, after exercise has produced profuse perspiration, and terminated in languor and fatigue; because in such circumstances the heat is not only sinking rapidly, but the system parts more easily with the portion that remains."—In short, it is a rule liable to no exception, that moderate exercise ought always to precede cold bathing, to promote the re-action of all the vessels and muscles, on entering the water; for neither previous rest, nor exercise to a violent degree, are proper on this occasion.
2. The duration of every cold bathing applied to the whole body, ought to be short, and must be determined by the bodily constitution, and the sensations of the individual; for healthy persons may continue much longer in it than valetudinarians; and both will be influenced by the temperature of the air, so that in summer they can enjoy it for an hour, when, in spring or autumn, one or two minutes may be sufficient.—Under similar circumstances, cold water acts on aged and lean persons with more violence than on the young and corpulent: hence the former, even in the hottest days of summer, can seldom with safety remain in the bath longer than a quarter of an hour; while the latter are generally able to sustain its impressions for double that time.
3. The head should first come in contact with the water, either by immersion, pouring water upon it, or covering it for a minute with a wet cloth, and then diving head foremost into the water.
4. As the immersion will be less felt when it is effected suddenly; and as it is of consequence that the first impression should be uniform over the body, we must not enter the bath slowly or timorously, but with a degree of boldness. A contrary method would be dangerous; as it might propel the blood from the lower to the upper parts of the body, and thus occasion a fit of apoplexy. For these reasons, the shower bath is attended with considerable advantages, because it transmits the water quickly over the whole body; and, consequently, is more consistent with the rules before-mentioned.
5. The morning is the most proper time for using the cold bath, unless it be in a river; in which case the afternoon, or from one to two hours before sun-set, will be more eligible; as the water has then acquired additional warmth from the rays of the sun, and the immersion will not interfere with digestion: on the whole, one hour alter a light breakfast,—or two hours before, or four hours after dinner, are the best periods of the day, for this purpose.
