Some travellers have thought that the ophthalmic disease in Kahira was occasioned by the fetid exhalations of the Chalige, and the drains; and have even observed, that those who are most severely affected in winter, recover as soon as the water has filled the Chalige and the pools. This is also a common idea with the natives. “The stink blinds me,” is a frequent expression on coming into a place of fetid odour; and it may be remarked, that the ordinary maxims of _indigenæ_ are rarely to be entirely disregarded. Whatever miasms however may issue from the canal, they cannot be equally dispersed over the city, as blindness is; and the Franks, Greeks, and other strangers who reside nearest this depôt of impurity, would be most affected if that were the cause. It may yet be one cause. Another I take to be the subtile dust above mentioned; but the most powerful, indiscreet exposure to the nocturnal air and dews. The collective influence of these is strengthened by the cloudless splendour of a vertical sun, reflected from the sterile expanse of sand, which offers no sombrous object on which the eye may repose itself. These considerations, it may be acknowleged, do not carry conviction; but too many local diseases are yet unexplained, to leave any wonder if the cause of this should yet remain problematical. _Plague._ All the improvements in the art of healing which modern Europe can boast as its own, are the result of more frequent experiment, and more patient and minute investigation, than existed in the antient. To conjecture ingeniously is a matter of small effort, and in treating of what is properly the object of experiment, it is not only of no value, but often of dangerous result. But it is suited to the indolence of the human mind, and flattering to personal vanity, which delights to perform much by a single energy. Hence, an hypothesis supported by some insulated fact, perhaps only by specious error, is often advanced with warmth, and the most important considerations militating against it, are forgotten, or warped to serve the purpose of the inventor. Thus the increase of the Nile was once confidently attributed to the Etesian winds; and the malady which has so often almost depopulated Kahira, is still by some imagined to proceed from the putrid deposition of its waters.