wonderfully improved that he could read a book of large print by passing his fingers along the lines. He was also a practical florist. But the most wonderful faculty which he possessed, was that of distinguishing sounds by the touch, being able to comprehend the greater part of a conversation when the mouth of the speaker was applied to his hand. The letter R, however, grated so much on his feelings, that his friends took care to avoid pronouncing it as often as possible. This feeling is distinct from the sympathetic thrilling occasioned by certain sounds felt all over the body. Mr. P. Knight says his very limbs were thrilled on hearing the commemoration of Handel at Westminster. Lackington, the celebrated bookseller, in his memoirs, mentions a lady, who, though deaf, took great delight in music, which, she said, she felt at her breast and in the soles of her feet. Of course we do not rest much on this instance, though it is not improbable. VFLOCITY OF SOUND. Sound is in this manner propagated, or travels in all directions from the place where it is produced. The quickness with which sound travels is much inferior to the quickness of light, which goes 95,000,000 miles, that is, it comes from the sun to the earth, in eight minutes and a half, while sound only goes 1142 feet in a second. By know ing this we can make near estimates of distances otherwise inaccessible. A thunder-cloud, for example, will be between six and seven miles distant if half a minute elapses from the time we see the lightning to the time we hear the thunder. The distance of a ship at sea is calculated in the same way, by attending to the difference of time observed between the flash and the report of her guns. It is another proof of the difference of wind and sound, that sound travels very nearly as quick against the wind as with it, though a contrary wind diminishes, and a fair wind increases its loudness. That sounds of different tones travel with the same velocity is evident from what we observe on listening to a peal of bells, or to any instrument of music; for all the tones come in succession to our ears, whereas if they did not travel at the same rate, they would be heard confusedly jarring with one another. The lowest whisper accordingly travels as rapidly as the loudest thunder. It is also to be remarked, that sounds proceed with the same velocity through a long or a short space, a large or a small distance. Sounds also travel with the same velocity by night and by day; in damp and in dry weather. This, how ever, is not to be understood as having the same effect on their loudness and lowness. Like the rays of light, sound is supposed to proceed in straight lines; though from its being greatly more reflexible than light, it can pass through the winding tube of a French horn, which light cannot do. Not only so, but the intensity of sound is much increased in the passage through a winding tube-a principle on which the speaking-trumpet is constructed. ECHOES. Like the rays of light also, sound can be reflected from certain bodies, and when this takes place it is called an echo, a word derived from the Greek. By taking advantage of the principle, echoes have been formed by art, as mirrors have been made for reflecting light. It was once thought that concave bodies were indispensable to produce echoes. A single flat wall, however, will produce an echo, and Le Cat says he has even observed that some convex bodies reflect sound, though a vault or a bending wall is the best form. PENETRATION OF SOUND. A third property, in which sound resembles. light, is its power of penetrating and passing through hard substances. Light passes through glass and diamonds, and sound in a similar manner passes through iron and other metals, as well as through wood. It may be also remarked, that, other circumstances being the same, the harder or more dense the substance, sound penetrates it the more easily, and in this respect it bears a strong resemblance to heat. When the ear is placed close to one end of a log of wood, however long it may be, and the other end struck or a watch applied to it, we are sensible of the sound of the watch or of the stroke, though it be too slight to be otherwise perceptible. When a piece of metal is applied to the bones of the head or to the teeth and struck, we also feel an indistinct sensation of sound, and this is felt even by those who are deaf to sounds conveyed through the air. The blind and deaf boy Mitchel, found his greatest pleasure in striking his teeth with a key, and was highly displeased when he was given a piece of wood as a substitute. CONDUCTORS OF SOUND. Wool, down, and feathers, are consequently bad conductors of heat, and also bad conductors of sound; though perhaps, there is no substance whatever through which sound will not pass more or less. The sound of the grand cataract of Niagara is found to be sensibly diminished when the ground is covered with snow, which, according to our principle, is a non-conductor of sound. Air, when very much rarefied, as in the exhausted receiver of an air-pump, will scarcely transmit sound at all; and it has hence been hastily concluded, that air is the only medium of sounds. It would, we think, have been more philosophical to have inferred that every substance whatever when rarefied, if that were possible, as much as the air in the exhausted receiver, would transmit sound with equal indistinctness. The clearness of sound, indeed, seems to depend very much on the density of the vehicle by which it is conveyed. In the cool of the evening, and still more as the night advances, when the air is no longer rarefied by the sun, we hear sounds, those for example of distant waters, which in the day are altogether imperceptible. The circumstance of sounds being more distinctly transmitted in cool air, has not escaped the observation of our poets. -Who the melodies of morn can tell, The wild brook babbling down the mountain's side; The pipe of early shepherd dim descried In the low valley. Echoing far and wide; |
