"It is to this fundamental property of the invari-

17

ability of the mass that we had always to come back. Philosophers and scholars long ago gave up seeking an exact definition of matter. The invariability of the mass of a given quantity of substance - that is to say, its coefficient of inertia measured by its weight, remained the sole irreducible characteristic of matter." [THE THEORY OF INTRA-ATOMIC ENERGY AND THE PASSING-AWAY OF MATTER.]

See Also

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constant of proportionality
Inertia
law of conservation of mass
law of constant composition
Mass
moment of inertia