May there not be light we cannot see? Gravitation is an unseen light; so too magnetism; electricity or its effect is sometimes visible, sometimes not. Besides these there may be more delicate forces not instrumentally demonstrable. A force, or a wave, or a motion--an unseen light--may at this moment be flowing in upon us from that unknown space without and beyond the stellar system. It may contain messages from thence as this pale visitant does from the sun. It may outstrip light in speed as light outstrips an arrow. The more delicate, the more ethereal, then the fuller and more varied the knowledge it holds. There may be other things beside matter and motion, or force. All natural things known to us as yet may be referred to those two conditions: One, Force; Two, Matter. A third, a fourth, a fifth--no one can say how many conditions--may exist in the ultra-stellar space, beyond the most distant stars. Such a condition may even be about us now unsuspected. Something which is neither force nor matter is difficult to conceive; the mind cannot give it tangible shape even as a thought. Yet I think it more than doubtful if the entire universe, visible and invisible, is composed of these two. To me it seems almost demonstrable by rational induction that the entire universe must consist of more than two conditions. The grey dawn every morning warns me not to be certain that all is known. Analysis by the prism alone has quite doubled the knowledge that was previously available. In the light itself there may still exist as much more to be learnt, and then there may be other forces and other conditions to be first found out and next to tell their story. As at present known the whole system is so easy and simple, one body revolving round another, and so on; it is as easy to understand as the motion of a stone that has been thrown. This simplicity makes me misdoubt. Is it all? Space--immeasurable space--offers such possibilities that the mind is forced to the conclusion that it is not, that there must be more. I cannot think that the universe can be so very very easy as this. BILLING AND SONS, LTD., PRINTERS, GUILDFORD End of Project Gutenberg's The Hills and the Vale, by Richard Jefferies