Here, in Fig. 3, are the real paths of Mars and the Earth, and also of Venus and Mercury. No loops, you see, in any of them, simply because we have set the sun in the middle. Set the earth in the middle, and each planet would have its own set of loops, each set enormously complicated, and all three sets mixed together in the most confusing way. It is well to remember this when you see, as in many books of astronomy, the old theory illustrated with a set of circles looking almost as neat and compact as the set truly representing the modern theory. For the idea is suggested by this simple picture of the old theory that the theory itself was simple, whereas it had become so confusing that not merely young learners, but the most profound mathematicians, were baffled when they tried to unravel the motions of the planets. I think the figure pretty well explains itself. All I need mention is, that while the shape and position of each path is correctly shown, the size of the sun at center is immensely exaggerated. A mere pin point, but shining with star-like splendor, would properly represent him. As for the figures of the earth and Mars, they are still more tremendously out of proportion. The cross-breadth of the lines representing these planets' tracks is _many times_ greater than the breadth of either planet on the scale of the chart. On September 5 the earth and Mars came to the position shown at E and M. You observe that they could not be much nearer. It is indeed very seldom that Mars is so well placed for observation. His illuminated face was turned toward the dark or night half of the earth, so that he shone brightly in the sky at midnight, and can be well studied with the telescope. When Galileo turned toward Mars the telescope with which he had discovered the moons of Jupiter, the crescent form of Venus, and many other wonders in the heavens, he was altogether disappointed. His telescope was indeed too small to show any features of interest in Mars, though the planet of war is much nearer to us than Jupiter. Mars is but a small world. The diameter of the planet is about 4,400 miles, that of our earth being nearly 8,000. Jupiter, though much farther away, has an immense diameter of more than 80,000 miles to make up, and much more than make up, for the effect of distance. With his noble system of moons he appears a remarkable object even with a small telescope, while Mars shows no feature of interest even with telescopes of considerable size. It was not, then, till very powerful telescopes had been constructed that astronomers learned what we now know about Mars.[4] [Footnote 4: See the "Moons of Mars" in "Letter Box" Department]