968  SAVART ON THE ELASTICITY OF CRYSTALLIZED BODIES. 
which the plates do not break clean off; for there is, it is well known, an 
obvious difference in the manner in which sulphate of lime breaks ac- 
cording to one direction or the other. We will, on concluding, re- 
mark, that these modes of division are precisely the same as those of a 
dise of rock crystal parallel to the axis and perpendicular to two faces 
of the hexahedron, and that the mean of the optic axes in sulphate of 
lime occupies in it the same position relatively to the nodal curves, as 
the projection of the single axis of rock crystal assumes in that of the 
plates of this substance of which we have just spoken. (See fig. 2, bis, 
No. 3.) 
The preceding researches are, doubtless, far from deserving to be 
considered as a complete examination of the elastic state of rock crystal 
and of carbonate of lime ; nevertheless we hope they will be sufficient 
to show that the mode of experiment we have employed may hereafter 
become a powerful means of studying the structure of solid bodies, 
regularly or even confusedly crystallized. Thus, for instance, the 
relations which exist between the modes of division and the primi- 
tive form of crystals allow us to presume that the primitive form of 
certain substances which do not at all yield to a mere mechanical 
division may be determined by sonorous vibrations. It is equally 
natural to think that less imperfect notions respecting the elastic state 
and cohesion of crystals than those we now possess, may throw light 
upon many peculiarities of crystallization: for example, it is not im- 
possible that the degrees of elasticity of a determinate substance may 
not be exactly the same, for the same direction referred to the primitive 
form, when the secondary form is different ; and, if it be so, as some 
facts induce me to suspect, the determination of the elastic state of 
crystals will lead to the explanation of the most complicated phzno- 
mena of the structure of bodies. Lastly, it appears that the comparison 
of the results furnished concerning the constitution of bodies, on the 
one hand by means of light, and on the other hand by means of sono- 
rous vibrations, ought necessarily to contribute to the progress of light 
itself, as well as to that of acoustics. 
