There have been instances on record of blind people who were able to discover colours by the touch; and deaf and dumb, who could feel sounds by placing their hand upon the speaker's mouth: this, however, is not more astonishing, than that the sense of smelling should be so acute, as to enable some persons to judge by it the quality of metals. Martial mentions a person, named Mamurra, who consulted only his nose, to ascertain whether the copper that was brought him were true Corinthian. There have been Indian merchants who, if a piece of money were given them, by applying their nose to it, defined its quality to a nicety, without touchstone, balance, or aqua-fortis. Europeans, also, are to be found whose sense of smelling is equally delicate and perfect. Marco-Marci speaks of a monk at Prague, who, when any thing was brought him, distinguished, by its smell, with as much certainty as the best nosed dog, to whom it belonged, or by whom it had been handled. It was also said of him, that he could accurately distinguish, in this manner, the virtuous from the vicious. He was much devoted to the study of natural philosophy; and, among other things, had undertaken to oblige the world with precepts on the sense of smelling, like those we have on optics and acoustics, by distributing into certain classes a great number of smells, to all of which he had given names; but an untimely death cut him off in the midst of these curious researches. The guides who accompany travellers on the route from Smyrna or Aleppo, to Babylon, have no other signs in the midst of the deserts, to discover their distance from the place of destination, than the smell of the sand alone, by which they determine with certainty. Perhaps they judge by the odour exhaled from small plants, or roots, intermixed with the sand. Physicians, in visiting the sick, have been known to form a prognostic, before having seen the patient, from the effluvia of the sick-room. Those who are in the habit of visiting the insane, know the peculiar odour that characterises that dire calamity; and it was remarked of the plague, that it had "a scent of the flavour of mellow apples." It is said that monkeys possess this power of discrimination in a very eminent degree. A story is told of a lady who had a pet of this description, whom she made her constant companion, and who suddenly, without any apparent cause, forsook her, and could not be persuaded to re-enter her chamber. The lady was at that time infected with measles, which shortly after appeared upon her; but, on her perfect recovery, the monkey returned to her with his usual familiarity. Some time after, the same lady caught cold, and was apparently very ill, but without fever. The monkey, as far as might be judged from his appearance, seemed to condole with his sick mistress, and to understand the difference of her distempers, by the confidence with which he remained in attendance upon her.