C.into another crystalline variety which is denser than water.
The statics of solids under high pressure is as yet, therefore, hardly drafted, but it seems to promise results which will not be identical with those obtained for the statics of fluids, though it will present at least an equal interest.
Sec.4.THE DEFORMATIONS OF SOLIDS If the mechanical properties of the bodies intermediate between solids and liquids have only lately been the object of systematic studies, admittedly solid substances have been studied for a long time.

Yet, notwithstanding the abundance of researches published on elasticity by theorists and experimenters, numerous questions with regard to them still remain in suspense.
We only propose to briefly indicate here a few problems recently examined, without going into the details of questions which belong more to the domain of mechanics than to that of pure physics.
The deformations produced in solid bodies by increasing efforts arrange themselves in two distinct periods.

If the efforts are weak, the deformations produced are also very weak and disappear when the effort ceases.

They are then termed elastic.

If the efforts exceed a certain value, a part only of these deformations disappear, and a part are permanent.
The purity of the note emitted by a sound has been often invoked as a proof of the perfect isochronism of the oscillation, and, consequently, as a demonstration _a posteriori_ of the correctness of the early law of Hoocke governing elastic deformations.