Page:Scientific Memoirs, Vol. 1 (1837).djvu/151

 Researches on the Elasticity of Bodies which crystallize regularly; by

(Read to the Academy of Sciences of Paris, January 26th, 1829.)

From the Annales de Chimie et de Physique, vol. . p. 5, et seq.

ITHERO precise notions respecting the intimate structure of bodies could be acquired only by two means: first by cleavage, for opake or transparent substances regularly crystallized; secondly, for transparent substances only, by the modifications which they occasion in the propagation of light.

The first of these means has taught us that crystallized bodies are collections of laminæ parallel to certain faces of the crystal; but it has given us no information respecting the force with which these laminæ adhere together nor their elastic state. The second, far more powerful than the first, because it renders evident actions depending on the very form of the particles, has given rise to the discovery of phænomena the existence of which cleavage alone would never have allowed us to suspect. But although these two experimental processes have introduced many new ideas and notions into the science, yet it may be said that the part of physics which treats of the arrangement of the particles of bodies, and the properties resulting from it, as elasticity, hardness, fragility, malleability, &c. is still in its infancy.

The investigations of Chladni respecting the modes of vibration of laminæ of glass or metal, and the researches which I have published on the same subject, especially those which relate to the modes of division of discs of a fibrous substance, such as wood, allow us to suspect that we might acquire by this means new notions respecting the distribution of elasticity in solid bodies; but it was not clearly seen by what process this result might be attained, though the road which it was necessary to follow was one of great simplicity.

But if this mode of experiment, which we are about to describe, is simple in itself, it is not the less surrounded by a multitude of difficulties of detail, which cannot be removed without numerous attempts; and I hope this will serve to excuse the incompleteness of these researches, which I only give as the first rudiments of a more extensive investigation.