in the "cusps" at the ends of the crescent occasional interruptions and irregularities are presented which have been interpreted as implying the existence of great mountains on Venus. But when this is admitted we have said almost all that has ever been alleged to be discernible by us of the topography of that globe which is really our nearest planetary neighbour. The little that we have seen merely suggests what a wonderful spectacle might be disclosed could we put Venus into a more favourable position. If Venus were placed where Mars is, then the greater size of the former planet would make it a far more striking spectacle than Mars ever can be. Mars happens to be the more interesting globe to us simply because it is better placed for observing. Everybody knows that you can read your book comfortably if you sit with the light so nearly behind you that it may fall on the page at which you are looking. This is the aspect in which Mars is presented at opposition. The sun, which illuminates Mars, is then at midnight, behind the observer, but its beams are directed full on the planet, and exhibit it under the most favourable conditions. But Venus is presented to us in quite a different manner. It is not pleasant to try to read with the lamp in front of you, and your book held up between you and the lamp. Yet this is the way we have to look at Venus when it makes its closest approach. The consequence is that, while astronomers have abundance to tell us about the appearance of Mars, they have but little to say about the features of that other globe which is both larger and nearer to us than Mars, and with which, in all probability, we have closer affinities than we have with any other body in the universe.
From one cause or another, it happens that Mars is the
