186 SENSORIAL FUNCTIONS. 



surface of a calm lake is thrown into circular waves by 

 the force of a stone thrown into it. 



The velocity of sound through the atmosphere is about 

 1100, or more nearly 1142 feet in a second. Hence we 

 see the flash of a gun, and after an interval depending 

 on the distance, hear the report. Thus in a thunder 

 storm, if we allow 1100 feet per second, between the 

 time when the flash of lightning is seen, and the thunder 

 heard, we may ascertain very nearly the distance of the 

 cloud. 



Solids and liquids convey sounds much more perfectly, 

 and rapidly, than air. Franklin found that a sound, 

 after travelling above a mile through water, lost little of 

 its intensity, and Chladni states, that according to his 

 experiments, the velocity of sound in water is at the 

 rate of about 4,900 feet in a second, being between four 

 and five times more rapid than it is through the air. 



In musical tones, if the intervals between the vibra- 

 tions be short, the tone is acute, if long, the tone \$ grave. 

 Hence in the violin, and other musical instruments, the 

 strings designed for high or acute notes are small, that 

 their vibrations may be rapid ; while those which make 

 the low, or grave tones are large, and sometimes wound 

 around with fine wire, in order to increase their weight, 

 and thus to make them vibrate slowly. 



In musical tones, it is the quality, and variety of the 

 sounds which give the hearer so much pleasure. The 

 string of the Harpsichord when fastened to a piece of 

 boaro^ or to the ground, may be made to give the same 

 pitch, or grade of tone, with respect to gravity or acute- 

 ness, as when on the instrument, but an instrument hav- 

 ing such a quality of tone, would give -no pleasure to 

 the Ear. 



The Ear is susceptible of much cultivation with 

 respect to music, as is the eye with respect to painting. 

 The finest and most complex strains of music are often 

 lost upon the uneducated Ear, as the noblest works of 

 the painter are unappreciated by the uncultivated eye. 

 Hence tones, and pictures, which raise the most enthu- 



In what direction is sound propagated 7 What is the velocity with 

 which sound passes through the air 7 How may we tell the distance of 

 a thunder cloud 7 What is said of the propagation of sound by solids 

 and fluids 1 How is grave or acute musical tones formed 1. 



