HEARING.

It has been said that the extent of a blind man's observation is confined to the space he can compass with his two arms; this is incorrect. The writer of the paragraph evidently forgot the power of the sense of hearing, which brings the mind into communication with very distant objects, and even possesses certain advantages over the sense of sight, e. g., by the ear objects may be perceived in the thickest darkness, whereas light is essentially necessary to enable the eye to perform its duties; then, again, the intervention of any opaque substance, be it ever so thin, renders sight useless, whereas the ear detects what is passing on the other side of a moderately thick wall. If it were not for man's ingenuity in producing artificial light, sight would be useless to the human race during half the span of existence, but hearing is ever active without the assistance of art.

Mr. Glaisher, in one of his balloon ascents, heard the roar of the London traffic when more than a mile above the city, and the sound of falling rain on trees when one thousand feet above the earth.

The way in which the American Indians make use of their ears on the prairies is too well known to need repetition. The report of large guns may be heard for several miles, and this has often given notice of a fierce fight, when the eye was altogether powerless in the matter.

Aristotle, who was physician to Alexander the Great, invented for his master a trumpet which was capable, it is said, of conveying orders to generals at the distance of one hundred stadia, about twelve miles.

Sound varies slightly in speed according to the density of the atmosphere, being more rapidly transmitted in warm than in frosty weather. The clearest voice to a deaf man is that which is deep and soft; and it has been remarked by a judicious writer that,

"We are hardly aware, until we have lost it, how much we rely on the sense of hearing to protect us from danger. How difficult it is, for example, to cross a London thoroughfare in safety by the aid only of the eyes; how much sound aids us in avoiding a crowd, a falling tile, a shutter rising out of the pavement, etc.!"

A German philosopher has said that while sight is the clearest, hearing is the deepest of the senses. The one is the favourite vehicle and stimulus of emotion, the other of intellect. Certainly music appeals more directly to feeling than painting: the tones of the voice are the truest expression of sentiment and character; the sounds of nature, the wailing and sighing of the wind, the notes of birds, the murmurs of bees affect the feelings more profoundly and mysteriously than colour and form.

THE EFFECTS OF DARKNESS AND SILENCE, BLIND
ANIMALS, ETC.

In the cave or grotto of Adelsberg, about thirty miles from Trieste, in Austria, the effect of darkness is shown in the production of a race of worms without eyes, called the Proteus anguinus; and the same kind of worm is found in the Mammoth Cave, in Kentucky, America, an account of a visit to which may not be uninteresting. A writer in the Chicago Tribune' gives an account of some observations made by Dr. H. Ralls Smith during a visit to the Mammoth Cave for purposes of scientific research. Dr. Smith reports the permanent inhabitants of the cave to be not only blind and deaf, but without eyes, or even the trace of an orbit or an optic nerve, and, it is presumed, without the organ of hearing. So much for the effects of the awful darkness and stillness of the cave upon its regular inhabitants! The effect is of the same kind on its occasional visitor. The following are the words

of the correspondent of the Chicago Tribune :-" Dr. Smith on one occasion penetrated about four miles into the interior of the cave, and, at some four hundred feet below the surface of the earth, remained 'solitary and alone' for a considerable length of time, in the midst of impenetrable darkness, and of a silence agonizing to a degree difficult of conception to those who have not made a similar experiment. The effect upon him, he states, was very distressing, and almost insupportable, resulting in a very perceptible, although temporary, defection of hearing and aberration of mind. The cause of this is, no doubt, to be attributed to the total absence of phenomena, such as vibrations of light, etc. etc., to which we are accustomed so as to render them a necessary stimulus for the proper preservation of the animal economy, as well as for the normal performances of the functions of the senses." The writer adds, "Persons who have been lost in the Mammoth Cave, for one, two, or three days, have always been found, when rescued, in a state of temporary insanity; and when approached by the party or parties sent to their relief, they invariably endeavoured to hide themselves, and thus elude observation." Supposing all this to be true, it suggests the lesson which the writer deduces from the facts, that it is bad for the eyes, or ears, or any other organ to be unused, or but partially subjected to the influence of its peculiar stimulus. It is very remarkable to find that by the exercise of some unknown power the Proteus can perceive when a light is near, and tries to avoid it. We believe that there are at present in the Dublin Museum four living specimens of the Proteus anguinus from the Mammoth Cave of Kentucky. These specimens somewhat resemble the shape of fish, and are described as being transparent, without colour, and possessing a total absence of visual organs. The natural powers of living beings deteriorate for want of exercise, the idle hand becomes weak, and sometimes it is even seized

with paralysis. The mental powers in like manner decay for want of use. In the Mammoth Cave is a race of blind rats with remarkably large eyes; all the other animals in the cave have no eyes, and this seems to show that the rats came originally from the surface of the earth, and that their progeny lost the power of sight on account of not using their

eyes.

THE SENSE OF TOUCH.

Touch is the only sense which pervades the whole body,-direct contact, however, is necessary for its exercise. The more sensitive parts of the body are the soles of the feet, the palms of the hands, the tips of the fingers, especially the fore-finger, the tip of the tongue, and the lips. Persons having thick skins or corpulent bodies possess the sense of touch to a less degree than those not having such developments. Some writers maintain that the touch of the negro is inferior to that of the white man, but as far as our experience goes we have found the African quite equal in this respect to members of the Circassian race. The soles of the feet are so sensitive that the nature of the ground over which a cultivated blind man walks can be felt through his boots.

The tip of the tongue is employed by many females without sight to press thread through the eye of a needle. The lips are so sensitive that they are often used to verify the perceptions of the fingers, and an anecdote is well authenticated of a West Indian negro girl who having lost the power of reading with her fingers, found, when in the act of kissing her embossed Bible, that she could read with her lips, which practice she afterwards followed. The present writer has tried this experiment with perfect success, but inconvenience of position, and interference with respiration will prevent

lips superseding fingers, notwithstanding that they possess superior sensibility.

It may be observed that although absence of sight gives increased power of touch, and also presents additional motives for its exercise, yet the sense of feeling may be cultivated to a very high degree by sighted persons. An anecdote is related of John Brown, the celebrated American champion of the negro, that when in England, happening to discourse of various qualities of wool, to the amazement of the company he undertook and successfully performed the feat of distinguishing by touch the most intricate differences of quality, he having at the same time a thick bandage over his eyes; and it may be remarked that one branch of the shoe-trade depends so entirely upon touch that it is called by the expressive name of blind-stabbing.' In surgery also, and many of the higher professions, and occupations, a practitioner with delicate touch has a decided advantage over his less fortunate competitors.

Telling colours with the fingers is a fallacy, which has become widely spread through the deception of interested persons. All that touch can do is to distinguish between surfaces; it cannot feel rays of light; and as colour is a combination of rays, and makes no alteration in the surface of an object, touch cannot deal with it. If the colouring matter employed in any operation possesses any tactual peculiarity, such peculiarity can be detected by the fingers, but the colour itself cannot be detected. If any one doubts this, let him colour water in several ways, putting each particular colour into a separate vessel, then challenge the colour-professor to put his hand into the various waters, and name their colours. The remarks on this subject by C. Bell, author of the celebrated work on the 'Hand,' are so apposite that we cannot forbear transcribing them. He says, "When an individual is deprived of the organs of sight, no power of attention,