[22] All our thoughts, theories, "laws," etc., may perhaps be said to _touch_ Nature--as the tangent touches the curve--at a point. They give a direction--and are true--at that point. But make the slightest move, and they all have to be reconstructed. The tangents are infinite in number, but the curve is one. This may not only illustrate the relation of Nature to Science, but also of Art to the materials it uses. The poet radiates thoughts: but he sets no store by them. He knows his thoughts are not true in themselves, but they _touch_ the Truth. His lines are the envelope of the curve which is his poem. [23] See the report of the joint meeting of the Royal Society and the Royal Astronomical Society, November 6, 1919, when Einstein's theory was discussed. [24] It is obvious that the Einstein theory, in which Time enters as a kind of fourth dimension in relation to Space, removes us at once out of the whole field of ordinary scientific reasoning and lands us, so to speak, in a new world. The nature of Space (or of the universal medium, whatever it is) in any region--its possible fundamental accelerations there, its "curvature" or non-Euclidean character, and so forth--is supposed, according to this theory, to vary with the amount of matter in, or density of, that region; and the movements of bodies are consequently supposed to take on the characters (accelerations, etc.,) which we ascribe to the action of Gravitation. Gravitation in fact in any region is the manifestation in Time of the attributes of the universal Medium in that region--which latter again is dependent on the degree of Matter present. Thus, Matter, Time, and Space are _one phenomenon_. The whole Einstein theory, in fact, is a device to present these three Protean and variable elements of all material existence (Matter, Time and Space) as so far involved and interlaced in each other that they form always an absolute and complete unity. As such the theory is no doubt suggestive, and along the line of future speculation: but it awaits corroboration. If corroborated it will point the way to a new conception of the Universe. [25] J. S. Mill. [26] See Stallo's excellent _Concepts of Modern Physics_. [27] See, for instance, the last new thing in this style--the Helmholtz molecule as improved upon by Sir William Thomson; it is described as follows: "A heavy mass connected by massless springs with a massless enclosing shell; or there may be several shells enclosing each other connected by springs with a dense mass in the centre (far more dense than the ether)." It is not, of course, seriously maintained that this nonsensical creation exists--but that if it did exist it would account for certain unexplained phenomena in the dispersion of light, etc. Later still (1920) we have the following delightful verdict on the Structure of the Atom, given by Sir Ernest Rutherford--and which I commend to all lovers of clear thinking:--