They can do so because the arrangement of material particles which constitutes a given simultaneity may be regarded, if we so wish, as a thin section of a four dimensional solid. We can say, then, that there are two sorts of time. First there is ordinary Physical "time" which is measured by the recurrence of three-spatial simultaneities and this, if we choose, may be regarded as produced by the passage across our space of something which has extension in four dimensions. Secondly, there is what I am inclined to call Subjective time, consisting of changes in Psychic states; and which may be regarded, provisionally, as being perceived by virtue of changes in "objects," including the vehicles of our own consciousnesses, in space of four dimensions, or, at any rate, in space of a dimensionality higher than three. I do not mean the foregoing remarks to be taken too literally for I do not regard three-dimensional change as produced by the passage across our space of actual four-dimensional solids. This seems to me to be altogether too crude an idea and was only introduced to bring out my point that three-dimensional change is _capable of expression_ in terms of four space. Whether it is solely a phenomenon of consciousness or whether there may be something in the nature of four-dimensional "lines of force" which cut three-dimensional space and determine material distributions I am not at all prepared even to surmise. A side light on this matter of the two sorts of time is given by the phenomena of time in dreams. It is well known that we may be awakened by a noise and that in the very few seconds between the occurrence of the noise and our becoming completely conscious we may experience a long and complicated dream in which we may do and say things which would take quite a long time in actual life and this without any sense of hurry. This seems to show that the "time scale" for the dream state is not the same as that to which we are accustomed in our waking hours. The difference should be sought, as Mr. Bragdon points out, in the differing vehicle of consciousness. This idea can be pushed much further. I have suggested that there is a sort of time which is, so to speak, peculiar to our space and which is expressible in terms of four space; and that there is another sort of time which appertains to four space itself, associated, that is, with four space change in the same way that three space time is associated with three space change. But if we accept the idea that there are more dimensions of space than three we cannot refuse to consider the possibility that there are more than four. If so we must say that four space change is in turn expressible in terms of five space in just the same way that three space change is expressible in terms of four space.