Page 157 of 212

The theory of gravitation derived in this way from the general

postulate of relativity excels not only in its beauty; nor in

removing the defect attaching to classical mechanics which was

brought to light in Section XXI; nor in interpreting the

empirical law of the equality of inertial and gravitational mass;

but it has also already explained a result of observation in

astronomy, against which classical mechanics is powerless.