There is a well in the neighbourhood of this town, which possesses a great many medicinal virtues; and though I have not been able to ascertain its mineral qualities, I have found, by using the water, that it is extremely friendly to the stomach, that it excites appetite and digestion, and lively spirits; that it is efficacious in the cure of gravel and nephritic complaints; and in cases of foulness of the blood, I have found it superior to any mineral waters I have met with in Europe. It has completely cured my Jew servant of a most inveterate scurvy, under which he had laboured for a very considerable time.
Notwithstanding the Moors possess this inestimable treasure near one of their most opulent and populous cities, yet, owing to fabulous tales, handed down by tradition from one generation to another, these superstitious people will never drink or disturb the water; to do so is reckoned sacrilege, and the offender is severely punished: for they positively affirm, that one of their great saints has been transmuted into it, and that at some distant period he will resume his natural form, to perform a great many miracles, and to render the Moors rich and happy, more so indeed than Mahomet has promised them in the other world.
While I have been here, I have had daily intercourse with the most eminent of their Tweebs. They pay me regular morning visits, questioning me on several points. One day I was asked by what means health was preserved, and what produced disease in the human body; I answered, that, "among several other remote causes, the air, by its different constitutions, had a great effect upon the human frame: that diseases revolve periodically, and keep time and measure exactly with the seasons of the year; and that either health or disease depended in some measure on the universal influence of the air, by its gravity, heat, cold, moisture, dryness, or exhalations." They have no idea of natural philosophy, nor of the knowledge and physiology of the air, or how to change and destroy its bad qualities in close and confined places. After much persuasion, I prevailed on some of them to make use of the fuming mixture of brimstone and aromatic ingredients, in all cases of pestilential fevers. Though this is not so efficacious as the nitrous acid, yet it will considerably abate the progress of contagion, and they are acquainted with the materials of the former, whereas they have not the smallest idea of the latter.