142 M. Sjtv^rt OH the Elasticity of 



Qla&ticity, the axis of greatest elasticity corresponding with the 

 axis of the branch, and the other two axes, which are equal, 

 being perpendicular to the annual layers of the wood. When 

 the branch is nearly cylindrical, the elasticity is sensibly uni- 

 form in all the diameters of a section perpendicular to the axis 

 of the branch. 



The following are some of the leading results obtained by 

 using plates of beech : — 



1 . When one of the axes of elasticity is in the plane of the 

 plate of wood, one of the nodal figures (viz. those taken by the 

 sand,) is always composed of two straight lines at right angles, 

 one of the lines being in the direction of the axis of elasticity. 

 The other figure is formed by two curves, like the branches of a 

 hyperbola, having their convex summits towards each other, 

 and equi-distant from the centre of the plate. 



2. When the plate does not contain any of the axes of elas- 

 ticity in its plane, the two nodal figures are always hyperbolic 

 curves. 



3. The number of vibrations which accompany each mode of 

 division is generally as much higher as the inclination of the 

 plate to the axis of greatest elasticity becomes less. 



4. The plate which emits the most acute sound, or which 

 is susceptible of producing the greatest number of vibrations, 

 is that which contains in its planes both the axis of greatest 

 elasticity > apd the axis of mean elasticity. 



5. The plate perpendicular to the axis of greatest elasticity 

 is that which emits the gravest sound, or produces the smallest 

 number of vibrations. 



6. When one of the axes is in the plane of the plate, and 

 when the elasticity in a direction perpendicular to this axis is 

 equal to that of th? ax,is itself, the two nod^l systems are si- 

 milar^ 1'hey are each composed of two straight Hnes at right 

 angles, and the one system is inclined 45° to the other. In 

 bodies with these inequal axes of elasticity, there are only two 

 planes which enjoy this property. 



M. Savart next proceeds to the analysis of rock crystal by 

 means of sonorous vibrations, and the following are the leading 

 results : — 



1. The elasticity of all the diametral lines of any plane what- 



