The philosophy of natural history / by William Smellie ... ; with an introduction and various additions ... by John Ware.

  • Smellie, William, 1740-1795.
Date:
1832
Catalogue details

Licence: Public Domain Mark

Credit: The philosophy of natural history / by William Smellie ... ; with an introduction and various additions ... by John Ware. Source: Wellcome Collection.

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    have been illustrated by comparing them to the little circular waves or undulations which are produced when a stone is thrown into stagnant water. Similar motions are probably produced in the air by the vibrations of sonorous bodies. The celerity with which sounds, or undulations of air, move, has been computed. All sounds, whether acute or grave, strong or weak, move at the average rate of 1142 feet in a second of time. Hence, whenever lightning, or the fire of artillery is seen, its distance may be ascertained by determin¬ ing the interval which elapses before the thunder, or the report is heard.* ‘ The force or intensity of sound is augmented by reflection from surrounding bodies. It is from this cause that the hu¬ man voice, or any other noise, is always weaker and less dis¬ tinctly heard in the open air than in a house. A mu'^ket discharged upon a wide and extensive plain, sounds but little louder than the burning of a squib, whilst among buildings or hills, where there are a thousand reverberations, its report is very loud.’ The modifications of sound are not less various than those of tastes or odors. The ear is capable of distinguishing some hundred tones in sound, and probably as many degrees of strength in the same tones. By combining these, many thou¬ sand simple sounds, which differ either in tone or in strength, are perceived and distinguished by the ear. A violin, a flute, a French-horn, may each of them give the same tone ; but the ear easily makes the distinction. The immense variety of sensations, arising from the organs of smelling, of tasting, and of hearing, enables animals to judge concerning the na¬ ture and situation of external objects. By habit we learn to know the bodies from which particular species of sound pro¬ ceed. Previous to all experience, we could not distinguish whether a sound came from the right or the left, from above or below, from a greater or a smaller distance, or whether it was the sound of a coach, of a drum, of a bell or of an animal. Hearing enables us to perceive all the agreeable sensations conveyed to our minds by the melody and harmony of sounds. This, to man at least, is a great source of pleasure and of innocent amusement. But some men are almost totally des¬ titute of the faculty of distinguishing musical sounds, and of * ‘ It has been lately ascertained that the velocity of sound is considerably affected by different states of the atraos])here and of the weather, and by the wind. The lowest rate of its velocity, is 1099, the highest 1164 feet per second.’