as indicated hij their Acoustic properties. 105 



present phenomena quite analogous to those of plates of wood, 

 or of rock-crystal differently inclined to their axes of elasticity 

 or their directions of cleavage. 



As these experiments have been repeated frequently, and 

 under different circumstances, we may consider it as certain 

 that a plate of metal always comports itself as if it belonged 

 to a crystallized system ; — but does it follow from this property 

 that metals are regularly crystallized ? This difficulty may 

 be solved by the same means by which it has been discovered. 

 As the distinctive character indeed of crystallized bodies con- 

 sists in this, that their structure is found exactly the same in 

 every part of the same plane, and for parallel planes taken in 

 any direction whatever in relation to the faces of the crystals, 

 it is clear that in order to recognize if a body is regularly crys- 

 tallized, it is sufficient — 



1. To cut different circular plates of the same diameter and 

 the same thickness, taken in the same plane, and to see if their 

 modes of division are parallel to one another, and emit the 

 $ame sounds. 



2. To take several parallel plates, and to see if their modes 

 of division correspond, and are accompanied with the same 

 sounds. I therefore cut out of a cylinder of lead which 

 ■weighed 15 kilogrammes, several plates of the same size. The 

 1st, 3d, 5th, 7th, and 9th, were perpendicular to the axis of 

 the cylinders ; and the 2d, 4th, 6th, and 8th, taken between 

 the preceding ones, passed through the axis, and were contained 

 in the same plane. These being examined, I found, 1. that 

 the modes of division of the last set of plates were far from 

 being the same, and from being accompanied with the same 



i ^ sounds. 2. That the modes of division of the first set of 

 plates were also very different, and were not accompanied with 

 the same sounds. As this experiment was often repeated, and 

 with tin as well as lead, with the same results, we may con- 

 clude, that a mass of metal, considered as a whole, does not 

 possess the properties of a crystallized body, though each of 

 the plates cut from it vibrate as if they belonged to a body of 

 this kind. 



If we examine the modes of division of a circular plate of 

 metal, one or two decimetres in diameter, and afterwards 



