"The permanence and, therefore, the indestructibility of mass, which one recognizes throughout the changes in matter, being the only characteristic by which this great unknown conception can be grasped, its importance necessarily became preponderant. On it the edifices of chemistry and mechanics have been laboriously built up." [THE THEORY OF INTRA-ATOMIC ENERGY AND THE PASSING-AWAY OF MATTER. page 17]
See Also
indestructibility of matter
Law of the Permanence of the Properties of Matter
PERMANENCE OF FORM AND MATTER