We owe to accident many valuable discoveries in medicine. It is said that several Indians, having used the waters of a lake in which a cinchona tree was growing, experienced the benefit which led to the use of the Peruvian bark; and the thermal properties of the baths of Carlsbad were first made known by the howling of one of Charles the Fourth's hounds, that had fallen in them in a hunt. It has been also observed, in various countries, that particular waters produced various morbid affections; and to this cause have been attributed goitres, cretinism, calculi, and other distressing diseases. The ancients dreaded the impurity of their rivers. The Romans boiled their water in extensive _thermopolia_, where not only potations were drunk hot, but occasionally refrigerated with ice and snow, and, when thus prepared, called _decocta_. Juvenal and Martial refer this custom to the Greeks. Herodotus informs us that the Persian monarchs were accompanied on their expeditions by chariots laden with silver vases filled with the water of the _Choaspes_ that had been boiled, and which was solely destined for the king's use: Athenaeus tells us that it was light and sweet. Many ancient coins and inscriptions have recorded these salutary properties of certain waters. This real or supposed efficacy was scarcely discovered before it became the domain of priests: and common rain or river water became valuable and sanctified when blessed by them: hence the introduction of lustral water. The fluid extracted from the gown of Mahomet is the sacred property of the sultan. The moment the fast of the Ramazan is proclaimed, this holy vestment is drawn from a gold chest, and, after having been kissed with due devotion, plunged in a vase of happy water, which, when wrung from the garment, is carefully preserved in precious bottles, that are sent by the monarch as valuable presents, or sold at exorbitant prices as cures for any and every disease. Thus were the good effects of ablution, especially in wounds, attributed to some secret charm or quality conferred upon it by clerical benediction or the legitimacy of princes. When a quack of the name of Doublet cured the wounded at the siege of Metz in 1553, the water he used was considered to have been of a mystic nature; and Brantome describes his treatment in the following words: "Durant le susdit et tant memorable siege, etait en la place un chirurgien nomme Doublet, lequel faisait d'estranges cures avec du simple linge blanc, et belle eau claire venant de la fontaine ou du puit; mais il s'aidait de sortileges et paroles charmees, et chacun allait a luy." This Doublet, no doubt, was acquainted with an ingenious treatise on gun-shot wounds, written by Blondi in 1542, in which he strongly recommended the use of cold water; but, as his recommendation was not founded on any miraculous quality, he was forgotten, while Doublet was considered a supernatural being. Previous