If we imagine our whole universe, with its observers, planetary orbits, instruments, and everything else, embedded in a jelly, and then distort the jelly and contents in any way, the numbers at which our planetary orbits (or rather their telescopic images) intersect our scales will be unaltered. Moreover, we could vary, in any manner, the times at which all objects (including the clock hands) occupied their distorted positions, and the hand of some clock near the point where the planetary image crossed the scale would record for this occurrence the same dial reading as before. An inhabitant of this distorted universe would be absolutely unconscious of the change. Now the General Theory of Relativity which expresses itself in slightly varied forms, amounts to satisfying a certain philosophical craving of the mind, by asserting that the laws of nature which control our universe ought to be such that another universe like the above, whose inhabitants would be unconscious of their change, would also satisfy these laws, not merely from the standpoint of its own inhabitants, but also from the standpoint of our measurements. In other words, this second universe ought to appear possible to us as well as to its inhabitants. Einstein decides to make his theory conform to this philosophical desire, and this greatly limits the modifications of clocks and scales which he permits himself for the purpose of representing gravitation. Further, if we express the alterations of the measures as functions of proximity to matter, velocity and so forth, our expressions for these alterations will include, as a particular case, that where matter is absent, although the scales and observer may still remain. Our alteration of the scales and clocks with velocity must thus revert, for this case, to that corresponding to the older theory of relativity, in order to avoid predicting that two observers, in uniform motion relative to each other in empty space, will measure different values for the velocity of light. In this way, the velocity of light comes to play a part in expressing the alterations of the measures. Even with these restrictions, Einstein was able to do the equivalent of finding an alteration of scales and clocks in the presence of matter which would account for our finding that the planetary motions take place very nearly in accordance with Newton's law. The new law has accounted with surprising accuracy for certain astronomical irregularities for which Newton's law failed to account, and has predicted at least one previously unknown phenomenon which was immediately verified. In conclusion, it may be of interest to state how the new law describes the motion of a particle in the vicinity of a body like the earth. The law amounts to stating that, if we measure a short distance, radially as regards the earth's center, we must allow for the peculiarity of our units by dividing by $$\sqrt{1-\frac{2mG}{c^2r}}$$