WATERS and baths are to be looked upon as factors accessory to climate, over which they may have a dominating therapeutic influence. Spas frequently specialise in the treatment of particular ailments, and should be classified not only according to type of climate, but also upon their therapeutic indications. Whatever the chemistry of medicinal waters, their effects are several and complex. The biochemical action of medicinal waters is perhaps of greater moment than hitherto generally believed. Calcium, iodine, bromine, iron, salines, sulphur all occur in readily assimilable form as a dilute solution of electrolyte in different spa waters, thereby providing a means of restoring to the individual what has been lost by dysfunction and disease. Medicinal springs and baths should be under a public control, ensuring regular analyses, purity, and the preservation of the natural amenities. These resorts should also provide a wide range of electrical, physical, and other accessory means of treatment for the re-education of body functions and structures. Britain being a most favoured land as to spas and health resorts, it is now generally recognised that there is seldom, if ever, medical necessity to winter abroad, unless it be to obtain by altitude, or by dry or sea air, a suitable climate for the tuberculous or asthmatic. On the other hand, there is no doubt that Continental or foreign travel, giving a complete change to body and mind, may often be beneficial in cases of mental strain and nervous trouble, producing a detachment from insular home prejudices, and encouraging an interchange of visits and courtesies from country to country.