77ie Limits of Natural Laiv. 45. 



Body matter in the aggregate is a temporary mode 

 of force. We cannot reason from matter in mass to 

 matter in all its forms. All modes of force, ponder- 

 able and imponderable, come under the universal 

 principle of the transference and equivalence of forces. 

 The ponderable may then become imponderable, and 

 the imponderable ponderable ; in which case gravity 

 must be accepted as no more than a temporary quality 

 attaching to certain changeable modes of force. As- 

 suming gravity to be an attribute universally of the 

 form of force we call matter, it is far from proved 

 that its law is constant. There is, according to Mr. 

 Spencer, a rhythm of motion in all moving force, from, 

 the vibrations of a tuning-fork to the oscillations of 

 the earth in its orbit., We cannot fix the range or 

 determine the limits of rhythmic movements. That 

 manifestation of force called gravity, instead of being 

 fixed, may be constant only in changing. It is not 

 unreasonable to suppose that the law of gravitation, 

 as we now express it, is true only for the present ; it 

 may be a mode of force at the moment of the return 

 of a curve of oscillation, and be true but for a brief 

 period of time. Carried into the past and future, it 

 may lead only to error. We are ephemera at best, 

 and the age of scientific knowledge is but a span. 

 In the line of the limitless sweep of cosmic forces we 

 cannot measure so much as an handbreadth ; and 

 our instruments are rude and clumsy, forbidding us to 

 hope for absolute exactness, even within our narrow 



