Page:Popular Science Monthly Volume 14.djvu/387

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373
MOLECULAR DYNAMICS.

stroyed; if the characteristic manifestations of life have disappeared, it is not because they are really extinguished, but because they have been one after another turned back by the paralyzing action of the poison. In that motionless body, back of that lack-lustre eye, with all these semblances of death, sensibility and mind still persist intact; what looks to be a dead carcass hears and knows all that goes on around it; it feels pain when its body is pinched or burned; it still has feeling and will, but it has lost the instrument needed for manifesting them. The movements which are most expressive are the earliest to disappear—first voice, then the movements of the limbs, those of the face and the thorax, and lastly the movements of the eyes.

Is it possible to conceive a more dreadful torture than that endured by a mind which thus witnesses the privation of its organs one after another, and shut up, as it were, in the fullness of life within a corpse?

 

MOLECULAR DYNAMICS.
By L. R. CURTISS.

DYNAMICS refers to force or power. It deals with the primary conceptions of energy in its relations to subjects that are susceptible of numerical estimation, such as time, space, and velocity. Or, again, dynamics is that branch of science which measures the energies producing motion as well as those produced by motion, and is divided into two parts—kinematics, which pertains to motion without regard to the bodies acted upon; and kinetics, which refers to the cause of energies whereby motion is given to bodies, each of which is the antithesis of static energy or energy at rest. Molecular dynamics has for its domain the actual working forces inherent in the atoms and molecules of matter. This branch of the subject bears the same relation to physics as the differential calculus does to mathematics, and by thus dealing with the physical molecules and atoms we are enabled to extend the kinetic chain of causation down toward the infinitely small with a certainty almost parallel to the accuracy with which the integral calculus defines the motion of the planets.

The text-books teach us that one of the properties of matter is inertia, including both that of rest and that of motion, the former being defined as the passive condition of bodies when at rest. This definition refers to matter as a mass. The new philosophy, however, teaches that, since molecular motion refers to the invisible movements of the particles of the mass, there is no such thing as complete rest of the ultimate particles of matter short of absolute zero of temperature, which, if universal, means total frigidity of every sun and orb in the universe.

The current of scientific thought tends to demonstrate that all the