as indicated by their Acoustic properties. 1 09 



to disturb the formation of the crystalline systems, and to de- 

 termine an uniformity of elasticity sufficiently great to cause 

 the plates which have undergone this change to emit only one 

 sound, and to have its nodal system composed of two hnes 

 occupying no longer a determinate position. It would be 

 both curious and important to examine if the metals whose 

 crystaUization has been thus disturbed are as tenacious as in 

 the opposite case, and to see if they do not acquire some new 

 properties which will facilitate their application to certain ope- 

 rations in the arts. 



Several causes, such as hammering, rolling, and annealing, 

 may alter in different degrees the distribution of elasticity in 

 metals, but none of these causes appear to be of a kind to 

 bring these substances into a state of homogeneity. The cir- 

 cular discs of lead, copper, tin, brass, diminished to three 

 quarters of their thickness by means of hammering, appear to 

 preserve very nearly the same properties which they had when 

 they were newly melted : Their different nodal systems had 

 only a slight change of aspect and of place, but the sounds 

 which accompanied them were still sensibly at the same dis- 

 tance from one another. 



The process of rolling appears to produce analogous effects, 

 but with this difference, that the crystalhne systems being con- 

 siderably elongated by this action in two directions perpen- 

 dicular to each other, it may happen that plates of great ex- 

 tent present a structure approaching much nearer to regulari- 

 ty. I may mention, for example, a plate of zinc seven or eight 

 decimetres long, and three or four broad, out of which I cut 

 ten or twelve circular discs of the same diameter, which affected 

 the same modes of division similarly directed in relation to 

 the sides of the plate, and accompanied with the same sounds, 

 so that we may suppose that the vvhole of this plate of metal 

 was crystallized regularly throughout its whole extent. 



The interval between the two sounds of each of its circular 

 plates was a semitone minor. One of the modes of division 

 was composed of two lines at right angles, and the other of 

 two branches of a hyperbola to which the preceding lines were 

 axes : In short, they comported themselves as if they had be- 

 longed to a body having three rectangular and unequal axes 



