Félix Savart

“ At the point where we have seen that the elasticities are equal in the direction of the axis, the two curves transform themselves into two straight lines which intersect each other rectangularly, after which they again separate; but their separation is effected in a direction perpendicular to that of their coalescence. The sounds of the hyperbolic system follow nearly the same course as those of the system of crossed lines, that is to say, they become higher in proportion as the plates more nearly approach being parallel to the axis of greatest elasticity ”

“ 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 impossible 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 ”

“ The elastic state of these plates cannot present such remarkable differences as those we have observed in the preceding series; for, being all cut round the axis of greatest elasticity, they can only contain in their plane that of least or that of mean elasticity, or lastly, those intermediate between these limits, which do not vary greatly from each other. ”

“ The transverse axis of the nodal curves always occurs in the direction of the least resistance to flexion; it hence follows, that when in a series of plates this axis places itself in the direction at first occupied by the conjugate axis, it is because the elasticity in this direction has become relatively less than in the other. ”

“ Circular plates which produce normal vibrations are susceptible of several modes of division; sometimes they are divided into a greater or fewer number of equal sectors, always even in number, which perform their vibrations in the same time; at other times they are divided into a greater or fewer number of concentric zones; and these two series of modes of division again may be combined together, so that the acoustic figures which result are circular lines divided into equal parts by diametrical nodal lines. ”

“ Thus, for instance, the relations which exist between the modes of division and the primitive 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. ”

“ But it is obvious, that to attempt such an investigation it would be necessary to base it on experiments made with a substance the three axes of which shall be accurately perpendicular to each other, which is not entirely the case in wood. ”