and gradual nature of the changes themselves. The lunar spectator will be presented with eclipses of the earth, and, according to the position of sea and land, _i.e._ of light and shadow, with phases of the earth.[343] In the same way Bruno applied his principle of similarity to show that from distant stars the earth would appear of uniform magnitude and unvarying position, while in the neighbourhood of other suns it and all the other planets would disappear. As matter is the same in kind throughout the universe, so it is subject everywhere to the same law of unceasing change:--"The sun in its rising never seeks twice the same point, all things by stress of the continuous flux are renewed, nor ever seek again the haunts they have left, nor is there any part of the earth which does not pass through every region, and a like force now carries each part in one direction or another, now drives it away; and if by chance any one revisit the centre, it is no longer in the same form, nor in the same connection (_ordine_)."[344] Not even the whole can ever be twice the same, since the order and arrangement of its parts are continuously changing. Even in things that seem ever to present the same face there is a latent alteration which time will bring to light. There would otherwise be nothing to prevent the whole of Nature being fixed, petrified, as it were, to all eternity. Yet the substance of things--the atom--is unchanging.[345] "All things are in flow; the parts of the earth, seas, and rivers vary their positions, by a certain ebbing and flowing order of Nature. As matter wanders, flowing in and out, now here, now there, so the forms travel through matter. For there is not any form which, once occupying a portion of matter, retains it always, nor any matter which, once obtaining a certain form, maintains it for ever. Hence it is that, matter always taking up one form or another, and having equal capacity for all, consequently by virtue of its eternity it must sometimes fall in with that which is able to bind it to itself for ever; if this were to happen, all things would be so constituted that there would be no alteration or difference in them."[346] [Sidenote: The Ether.]