Most of us have vague ideas about small portions of time; so much so, that it is rather surprising to find to how many intelligent people, a second, as seen on the clock face, is its least conceivable interval. Yet a second has not only a beginning, middle, and end, as much as a year has, but can, in thought at least, be divided into just as many numbered parts as a year can. Without entering on a disquisition about this, let us try to show by some familiar thing that we can at any rate not only divide a second in imagination into, let us say, a hundred parts, but that we can observe distinctly what is happening in such a short time, and make a picture of it,--a picture which shall be begun and completed while this hundredth of a second lasts. Every one has fallen through at least some such a little distance as comes in jumping from a chair to the floor, and most of us, it is safe to say, have a familiar impression of the fact that it takes, at any rate, less than a second in such a case from the time the foot leaves its first support till it touches the ground. Plainly, however large or small the fall may be, each fraction of an inch of it must be passed through in succession, and if we suppose the space to be divided, for instance, into a hundred parts, we must divide in thought the second into at least as many, since each little successive space was traversed in its own little interval of time, and the whole together did not make a second. We can even, as a matter of fact, very easily calculate the time that it will take anything which has already fallen, let us say one foot, to fall an inch more; and we find this, in the supposed instance, to be almost exactly one one-hundredth of a second. On page 243 is a reproduction of a photograph from Nature, of a man falling freely through the air. He has dropped from the grasp of the man above him, and has already fallen through some small distance,--a foot or so. If we suppose it to be a foot, since we can see that the man’s features are not blurred, as they would undoubtedly have been had he moved even much less than an inch while this picture was being taken, it follows, from what has been said, that the making of the whole picture--landscape, spectators, and all--occupied not _over_ one one-hundredth of a second. We have given this view of “the falling man” because, rightly understood, it thus carries internal evidence of the limit of time in which it could have been made; and this will serve as an introduction to another picture, where probably no one will dispute that the time was still shorter, but where we cannot give the same kind of evidence of the fact.