Curiosities of Sound. 45 



the sea, and if a speaker or singer were placed in such an 

 apparatus, his voice might be heard at great distances by 

 persons situated within the boundaries of the cone. 



The velocity of sound propagated through air at the 

 freezing temperature is 1089 feet per second, and at 26.6° Cent., 

 or 78.8° F., 1140 feet.* If the elasticity remains the same, 

 augmentation of the density of air or gas diminishes the 

 velocity of sounds. Hydrogen gas, which is as elastic as air, 

 and much lighter, is consequently more favourable to the 

 rapid transmission of sonorous effects. 



At the freezing temperature, hydrogen transmits sound at 

 the rate of 4164 feet per second, or nearly four times as fast 

 as air, while carbonic acid does so at the much lower rate of 

 858 feet per second. Water conducts sound with more than 

 four times the velocity of air; pine wood, along its fibres, ten 

 times as fast ; and iron, seventeen times as fast. 



The elasticity of air is increased by raising its tempera- 

 ture, and as air opposes a certain resistance to the passage of 

 a sound-wave, its temperature is actually raised a little by its 

 stoppage of a quantity of motion, and its conversion into heat. 

 From this cause air conducts sound a little quicker than was 

 originally calculated by Newton, who did not take into account 

 this curious cause of its change of temperature. 



The ear is pleased with the regular recurrence of im- 

 pulses, and with the succession of sounds, or their combina- 

 tion, according to certain principles of proportion. Noises as 

 distinguished from musical sounds are wanting in regu- 

 larity, and discords lack the desired proportions. All 

 sounds consist in a series of pulsations, and if they are to 

 form musical notes, they must be quick enough to give 

 the sense of continuity to the ear, and not too quick to 

 be audible — a matter explained in a former paper, which 

 we published, entitled, " Sounds we Cannot Hear.^f Sounds 

 may be too deep for a particular human ear, or for any human 

 ear, and they may be too shrill. It is only a small part of 

 the entire music of nature that we can hear, but our range 

 is fortunately considerable, being from 16 to 38,000 

 vibrations in a second. The lowest notes are, however, 

 imperfect, and do not sound well alone, and the highest are 

 above those used in orchestral compositions, the practical 

 range being comprised between 40 and 4000 vibrations in a 

 second. 



* The relation of the Telocity of sound to the elasticity and density of the 

 air, or other medium, is thus expressed: — " The velocity is directly proportional 

 to the square root of the elasticity of the air, and inversely proportional to the 

 square root of the density of the air." 



t Vol. viii. p. 413. 



