The concepts and theories of modern physics / By J.B. Stallo.

  • John Stallo
Date:
1900
Catalogue details

Licence: In copyright

Credit: The concepts and theories of modern physics / By J.B. Stallo. Source: Wellcome Collection.

    137/376 (page 87)
    Wlien a pound of carbon is burned, tlie balance demon- strates the continuing existence of this pound in the carbonic acid, which is the product of coiiibustion, and from which the original weight of carbon may be re- covered. The quantity of matter is measured by its weight, and this weight is unchangeable. Sucli is the fact, familiar to every one, and its in- terpretation equally familiar. To test the correctness of this interpretation, we may be permitted slightly to vary the method of verifying it. Instead of burning the pound of carbon, let us simply carry it to the sum- mit of a mountain, or remove it to a lower latitude ; is its weight still the same ? Relatively it is ; it will still balance the original counteqwise. But the “ absolute weight ” is no longer the same. This appears at once, if we give to the balance another form, taking a pendu- lum instead of a pair of scales. The pendulum on the mountain or near the equator swings more slowly than at the foot of the mountain or near the pole, for the reason that it has become specifically lighter by being farther removed from the center of the earth’s attrac- tion, in conformity to the law that the attractions of bodies vary inversely as the squares of their distances. It is thus evident that the constancy, upon the ob- servation of which the assertion of the indestructibility of matter is based, is simply the constancy of a relation, and that the ordinary statement of the fact is crude and inadequate. Indeed, while it is true that the weight of a body is a measure of its mass, this is but a single case of the more general fact that the masses of bodies are inversely as the velocities imparted to them by the action of the same force, or, more generally still, in- vei-sely as the accelerations produced in them by the same force. In the case of gravity, the forces of attrac-