“Science,” says our author, “teaches us that, whenever a shock or pressure of any sort is suddenly applied to material of any nature, whether metal, wood, gas, water, air, etc., it is immediately affected in all its parts, from the point of contact to the whole extent of the material, in displacing and replacing the particles of a _determinate volume_; and the velocity of the movement of the particles of the mass, created by the concussion of shocks or pressure, depends _solely_ (?) upon its elasticity and density. Sound likewise _causes_ motions (?) with every particle of the air, and as far as the motion reaches; so that each particle, with regard to that which lies immediately beyond it, is in a progress of rarefaction during return.” What is meant by affecting a mass of matter “_in all its parts_,” by “displacing and replacing the particles of a _determinate volume_,” we do not precisely understand. That whatever causes motion does it “as far as the motion reaches,” is as unquestionable as any other identical proposition. But that the velocity of the movement of the particles, created by the concussion of shocks, pressure, _upon an unconfined elastic fluid_, depends _solely_ upon its elasticity and density, we dispute. That _pulses_ “are propagated from a _trembling body_ all around in a _spherical_ manner” may be true, if the air is on all sides equally elastic. Such might be the case with those produced by the vibrations of a _bell_, when the surrounding air is undisturbed by other causes, and is uniformly elastic at equal distances from it. It would not be strictly true if the initial pulse were made only in a certain direction. “Every impression made on a fluid is propagated every way throughout the fluid, whatever be the direction wherein it is made;” but it is not true that the impressions are equal at equal distances from the initial pulse, irrespective of its _direction_. This result would presuppose a fluid _perfectly_ elastic; which we never have--and _then_ we might, with equal truth, say that the impressions would be equal at all distances.