OF SOUND AND HEARING. 229 



divides the other air. But concerning this kind of elision 

 of the air, which happens when the percussion of air 

 against air createth sound, as in the voice, let inquiry be 

 made further. 



It is well doubted, whether the percussion that produces 

 sound, when the air is percussed by a string, or otherwise, 

 be from the beginning, when the string starting back per 

 cusses the air, or a little after, the air to wit being com 

 pressed by the first percussion, and thereafter acting the 

 part, as it were, of an hard body. 



When sound is yielded by the percussion of air against 

 air, it is required that there be an imprisoning or penning 

 of the air in some concave, as in whistling by the mouth, 

 in pipes, in the viol, in the voice ; which is divided, where 

 the air is penned in the hollow of the mouth or throat. In 

 the percussion of an hard body against air is required 

 hardness of the body and quick motion, and sometimes 

 communication with a concave, as in the cittern, lute, 

 beating of the air, &c. ; but in the percussion of an hard 

 body against an hard body, the hollow, or the quick motion, 

 is less required. 



There is a talk of a white gunpowder, which should give 

 percussion without noise. It is sure that nitre, which is 

 white, is of great force for expulsion, yet in such wise as 

 the speedy kindling doth much enhance both the percus 

 sion and the noise; but the quick kindling is caused 

 specially by the coal of willows, which is black. There 

 fore if a composition were made of sulphur and nitre, and 

 a modicum of camphor, it is like that the kindling would 

 be slower, and the percussion not so jarring and sharp; 

 whence much might be diminished of the sound, but with 

 loss too in the strength of the percussion. To be further 

 inquired. 



OF THE LASTING OF SOUND, AND ITS PERISHING AND 

 EXTINCTION. 



The lasting of the sound of a bell that is struck, or of a 

 string which seems to be prolonged, and gradually to fade, 

 comes not rightly of the first percussion, but the trembling 

 of the body percussed generates in the air continually new 

 sound. For if that trembling be checked, and the bell or 

 string stayed, the sound quickly dies; as in virginals, 

 where if the quill be dropped so that it touch the string 

 the sound ceases. 



