VISITS TO THE MOON AND PLANETS
they go; and it is only at the end of the first book that they really get started.
However, here we are now started; and if we are not exactly arrived on Mars, we are as near Mars as the telescope will take us; let us say about a thousand times nearer than our eyes can take us. I told you that the telescope would magnify as much as you like, but that you might not be satisfied with the result if you magnified too much. Roughly speaking, the best telescopes we have will magnify about a thousand times, so that we reduce the distance of Mars to about one thousandth of the actual distance, let us say 50,000 or 100,000 miles; and that is as near as the telescope will take us. One peculiarity of a telescope is that it usually turns things upside down, so that the South appears at the top. The white patch at the top of the picture is therefore not the North polar cap but the South polar cap. I wonder whether any one is at present making a South Polar Expedition in Mars? It is claimed that the white patch represents ice and snow, such as we have' at the poles of our Earth; others, however, question whether it can be ice and snow, because certain observations made with the spectroscope render it a little doubtful whether there is sufficient water in the air of Mars to make ice and snow at the Poles. One thing we know with certainty; that in the Martian Summer the cap diminishes in size as though it were ice and snow melting, and in the Winter it increases in size as though it were ice and snow forming. But, after all, other things besides water may give this appearance. At the end of the lecture, when we come to an experiment or two, we shall see