fect entire circle of that matter or colour, and not a part of a circle in motion. § 9. The Train of Ideas has a certain degree of Quick nefs. HENCE I leave it to others to judge, whether it be not probable that our ideas do, whilft we are awake, fucceed one another in our minds at certain distances, not much unlike the images in the infide of a lanthorn, turned round by the heat of a candle. This appearance of theirs in train, though perhaps it may be fometimes fafter and fometimes flower, yet, I guess, varies not very much in a waking man. There seem to be certain bounds to the quickness and flowness of the fucceffion of thofe ideas one to another in our minds, beyond which they can neither delay nor haften. $10. THE reason I have for this odd conjecture, is from obferving, that in the impreffions made upon any of our fenfes, we can but to a certain degree perceive any fucceffion; which, if exceeding quick, the fense of succeffion is loft, even in cafes where it is evident that there is a real fucceffion. Let a cannon bullet pafs through a room, and in its way take with it any limb, or fleshy parts of a man, it is as clear as any demonftration can be, that it muft ftrike fucceffively the two fides of the room: It is also evident, that it must touch one part of the flesh firft, and another after, and so in fucceffion; and yet I believe nobody who ever felt the pain of such a shot, or heard the blow against the two diftant walls, could perceive any fucceffion, either in the pain or found of so swift a ftroke. Such a part of duration as this, wherein we perceive no fucceffion, is that which we may call an infant, and is that which takes up the time of only one idea in our minds, without the fucceffion of another, wherein therefore we perceive. no fucceffion at all. § II. THIS alfo happens, where the motion is fo flow as not to fupply a conftant train of fresh ideas to the fenfes, as fast as the mind is capable of receiving new ones into it; and fo other ideas of our own thoughts, having room to come into our minds, between thofe offered to our fenfes by the moving body, there the fenfe of motion is loft; and the body, though it really moves, yet not changing perceivable diftance with fome other bodies as fast as the ideas of our own minds do naturally follow one another in train, the thing seems to stand still, as is evident in the hands of clocks and fhadows of fundials, and other conftant but flow motions; where, though, after certain intervals, we perceive by the change of distance that it hath moved, yet the motion itself we perceive not. § 12. This train the Measure of other Succeffions. So that to me it feems, that the conftant and regular fucceffion of ideas in a waking man, is, as it were, the meafure and standard of all other fucceffions, whereof if any one either exceeds the pace of our ideas, as where two founds or pains, &c. take up in their fucceffion the duration of but one idea, or else where any motion or fucceffion is fo flow as that it keeps not pace with the ideas in our minds, or the quickness in which they take their turns; as when any one or more ideas, in their ordinary course, come into our mind, between those which are offered to the fight by the different perceptible distances of a body in motion, or between founds or fmells following one another, there alfo the fenfe of a constant continued fucceflion is loft, and we perceive it not but with certain gaps of reft between. § 13. The Mind cannot fix long on one invariable Idea. If it be fo that the ideas of our minds, whilst we have any there, do conftantly change and fhift in a continual fucceffion, it would be impoflible, may any one fay, for a man to think long of any one thing. By which, if it be meant that a man may have one felf-fame hingle idea a long time alone in his mind, without any variation at all, I think, in matter of fact, it is not poffible; for which (not knowing how the ideas of our minds are framed, of what materials they are made, whence they have their light, and how they come to make their appearances) I can give no other reason but experience; and I would have any one try whether he can keep one unvaried fingle idea in his mind, without any other, for any confiderable time together. § 14. FOR trial, let him take any figure, any degree of light or whitenefs, or what other he pleases, and he will, I fuppofe, find it difficult to keep all other ideas out of his mind; but that fome, either of another kind, or various confideration of that idea (each of which confiderations is a new idea), will conftantly fucceed one another in his thoughts, let him be as wary as he can. $15. ALL that is in a man's power in this cafe, I think, is only to mind and obferve what the ideas are, that take their turns in his understanding, or elfe to direct the fort, and call in fuch as he hath a defire or use of; but hinder the conftant fucceffion of fresh ones, I think he cannot, though he may commonly choose whether he will heedfully observe and confider them. § 16. Ideas, however made, include no Senfe of Motion. WHETHER these several ideas in a man's mind be made by certain motions, I will not here difpute; but this I am fure, that they include no idea of motion in their appearance; and if a man had not the idea of motion otherwife, I think he would have none at all; which is enough to my present purpose, and fufficiently shows, that the notice we take of the ideas of our own minds, appearing there one after another, is that which gives us the idea of fucceffion and duration, without which we should have no such ideas at all. It is not then motion, but the conftant train of ideas in our minds, whilft we are waking, that furnishes us with the idea of duration, whercof motion no otherwife gives us any perception, than as it caufes in our minds a conftant fuccellion of ideas, as I have before fhowed; and we have as clear an idea of fucceffion and duration, by the train of other ideas fucceeding one another in our minds, without the idea of any motion, as by the train of ideas caufed by the uninterrupted fenfible change of distance between two bodies, which we have from motion; and therefore we fhould as well have the idea of duration, were there no fenfe of motion at all. 17. Time is Duration fet out by Meafures. HAVING thus got the idea of duration, the next thing natural for the mind to do, is to get fome measure of this common duration, whereby it might judge of its different lengths, and confider the distinct order wherein feveral things exift, without which a great part of our knowledge would be confufed, and a great part of history be rendered very useless. This confideration of duration, as fet out by certain periods, and marked by certain measures or epochs, is that, I think, which moft properly we call time. § 18. A good Measure of Time muft divide its whole Duration into equal Periods. In the measuring of extenfion, there is nothing more required but the application of the standard or measure we make use of to the thing, of whofe extenfion we would be informed. But in the measuring of duration this cannot be done, because no two different parts of fucceffion can be put together to measure one another; and nothing being a measure of duration but duration, as nothing is of extenfion but extenfion, we cannot keep by us any standing unvarying measure of duration, which confifts in a conftant fleeting fucceffion, as we can of certain lengths of extenfion, as inches, feet, yards, &c. marked out in permanent parcels of matter. Nothing then could ferve well for a convenient measure of time, but what has divided the whole length of its duration into apparently equal portions, by conftantly repeated periods. What portions of duration are not diftinguished, or confidered as diftinguished and measured by fuch periods, come not fo properly under the notion of time, as appears by fuch phrafes as thefe, viz. before all time, and when time fhall be no more. 19. The Revolutions of the Sun and Moon the propereft Measures of Time. THE diurnal and annual revolutions of the fun, as having been, from the beginning of nature, conftant, regular, and univerfally obfervable by all mankind, and fuppofed equal to one another, have been with reafon made use of for the measure of duration. But the diftinction of days and years having depended on the motion of the fun, it has brought this mistake with it, that it has been thought that motion and duration were the measure one of another; for men, in the measuring of the length of time, having been accustomed to the ideas of minutes, hours, days, months, years, &c. which they found themselves upon any mention of time or duration prefently to think on, all which portions of time were measured out by the motion of those heavenly bodies, they were apt to confound time and motion, or at least, to think that they had a neceffary connection one with another; whereas any conftant periodical appearance, or alteration of ideas in feemingly equidistant spaces of duration, if conftant and univerfally obfervable, would have as well diftinguished the intervals of time, as those that have been made ufe of; for fuppofing the fun, which fome have taken to be a fire, had been lighted up at the fame diftance of time that it now every day comes about to the fame meridian, and then gone out again about twelve hours after, and that in the space of an annual revolution it had fenfibly increafed in brightnefs and heat, and fo decreased again; would not fuch regular appearances ferve to measure out the distances of duration to all that could obferve it, as well without as with motion? For if the appearances were conftant, univerfally obfervable, and in equidiftant periods, they would ferve mankind for meafure of time as well, were the motion away. 20. But not by their Motion, but periodical Appear ances. FOR the freezing of water, or the blowing of a plant, returning at equidiftant periods in all parts of the earth, would as well ferve men to reckon their years by as the motions of the fun; and in effect we fee, that fome people in America counted their years by the coming, of certain birds amongst them at their certain feafons, and leaving them at others. For a fit of an ague, the fense of hunger or thirst, a fmell or a tafte, or any |