of the new planet, which was called Neptune. The marvel is that by pure reasoning the mind of man could have achieved such results. If the observation of Uranus is difficult, how much more that of Neptune, which is still further plunged in space! Yet by patience a few facts have been gleaned about him. He is not very different in size from Uranus. He also is of very slight density. His year includes one hundred and sixty-five of ours, so that since his discovery in 1846 he has only had time to get round less than a third of his path. His axis is even more tilted over than that of Uranus, so that if we compare Uranus to a top held horizontally, Neptune will be like a top with one end pointing downwards. He rotates in this extraordinary position, in the same manner as Uranus--namely, the other way over from all the other planets, but he revolves, as they all do, counter-clockwise. Seen from Neptune the sun can only appear about as large as Venus appears to us at her best, and the light and heat received are but one nine-hundreth part of what he sends us. Yet so brilliant is sunshine that even then the light that falls on Neptune must be very considerable, much more than that which we receive from Venus, for the sun itself glows, and from Venus the light is only reflected. The sun, small as it must appear, will shine with the radiance of a glowing electric light. To get some idea of the brilliance of sunlight, sit near a screen of leaves on some sunny day when the sun is high overhead, and note the intense radiance of even the tiny rays which shine through the small holes in the leaves. The scintillating light is more glorious than any diamond, shooting out coloured rays in all directions. A small sun the apparent size of Venus would, therefore, give enough light for practical purposes to such a world as Neptune, even though to us a world so illuminated would seem to be condemned to a perpetual twilight. CHAPTER VII THE SUN