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September 18, 1891.] THE PHOTOGRAPHIC NEWS. 655 stars belong to the galactic system, but the large proper motion of some stars, taken in conjunction with their small parallax, affords evidence, as Prof. Simon Newcomb has pointed out, that they will in time pass away from our galaxy. Prof. Simon Newcomb has shown in his “ Popu lar Astronomy ” that, making the most liberal assumptions as to the number and masses of the stars of our galactic system, the highest speed which a body could attain if it fell from an infinite distance through such a stellar system would be twenty-five miles a second, a velocity which is certainly smaller than that of many stars. The regions outside our galaxy cannot, therefore, be absolutely barren, but however sparsely luminous stars are distributed through space, if there were no absorption of light in its passage through the ether, and no opaque bodies to blot out the line of distant stars, it would be impossible, as Olbers long ago pointed out, to draw a line in any direc tion which would not in an infinite universe pass through some luminous star, and the whole heavens ought to shine with the average brightness of such stars. That the heavens are comparatively dark may, there fore, be taken as proof either that the light-transmitting ether is not perfectly elastic, or that there are numerous dark bodies in space that blot out the light which we should otherwise derive from the more distant parts of the universe. TALKING WITH THE STARS. When Professor George Davidson, of the Davidson Observatory and the Coast and Geodetic Survey, was shown the Paris cablegram saying that an old lady had just died at Spa, leaving 100,000 fr. as a prize to the astronomer, French or foreign, who within ten years shall be able to communicate with any planet or star, he read it through slowly once, then he read it twice more rapidly. Finally, he picked it up, held it at the proper distance from his eyes, and squinted at it just as he would squint at Mercury through his telescope if he wanted to find the big tortoise-shaped spot on its northern hemisphere. “ An old lady ! an old lady !” the astronomer finally exclaimed. “ Now, isn’t that a pretty way to treat such a piece of phil anthropy as that ? An old lady, indeed ! Now, why under the sun do you suppose they keep back her name ? I am in clined to believe that some good-looking young man—one of these smooth talkers — has been getting close to her and talking a lot of astronomy into her ear. From the very form her bequest takes I am aware that somebody—Flammarian or some other man—has been talking to her about the proposed tri angle. The project is a very curious one, but can be explained quite easily.” Professor Davidson picked up a blue pencil and drew on a white sheet of paper a right-angled triangle. “ This that I have drawn,” he said, “is the old triangle of Pythagoras. That triangle has a right-angle, and the square built upon the side opposite the right-angle is equal to the sum of the squares built Upon the other two sides. The proposition is said to be the fundamental one of geometry. It has been proposed to draw such a figure as that in the Desert of Sahara, or some other great plain, the lines, of course, to be hundreds of miles long, and made so that they would be distinct in the desert sand. One way would be to plant palm trees so that the forests would take the shape of lines in the figure. Certainly, the green of the palms would be so bright in the contrast with the white of the sand that the drawing, when completed, would be plain enough. These are the suppositions that go along with the idea. It is supposed that there are people on some of the planets—at least, on Mars. It is supposed that the people on the planet are civilised and capable of looking through tele scopes, and it is concluded that if this is so, they must know the Pythagorean proposition. So, if the people of Mars look through their telescopes at the earth, they will be sure to see that enormous figure on the desert, and, seeing it, they will realise that the earth is inhabited by men of knowledge, and that the drawing is a signal; then, of course, they will set to work to answer it by building just such a figure on Mars. That will be talking from star to star. " But all this is bosh and nonsense to me, and I daresay it was bosh and nonsense to the man who wheedled the French woman into setting aside her 100,000 fr. But whoever he was, he knew on which side his bread was buttered, and knew that such a trust, for whatever purpose, would bear interest; but even supposing that the Desert of Sahara is one great plain, and that it is large enough for the purpose, and even supposing that it was possible to make such an enormous figure, I am in doubt whether the people on Mars, with such telescopes as we use, would be able to see it. At certain times, Mars is but 34,000,000 miles from the earth ; but it gets further and further away, until the distance is 61,800,000 miles. That is a good way off to see triangles ; but if Mars is inhabited, I am inclined to believe that the inhabitants are not fools. If they saw a triangle-shaped object on the face of the earth, they would not jump to the chimerical conclusion that there were idiots enough down here to build such an affair. The truth is, we do not know whether any of the planets besides the earth are inhabited. We think we know that it might be possible for men to live on Mercury. The situation and condition of things on the other planets are altogether different from those on the earth. So when we talk about the inhabitants of the planets we enter the realm of surmise, and M. Jules Verne has a better chance than the scientist. The four planets nearest the sun are Mercury, Venus, the Earth, and Mars. Mercury is only 35,392,000 miles from the sun, which is not very far when you take the heat into consideration. Consequently, we believe it is a good many times hotter than Arizona on Mercury. There are other disadvantages, such as a lack of space, enor mous mountains, and no certainty of atmosphere. Mercury is only 3,060 miles in diameter, yet there are mountains on its surface over twelve miles high. “Venus is 66,134,000 miles from the sun, and is plenty hot enough, although nearly twice as far as Mercury from the great heater. Then there is some question about the atmosphere as yet, and the year is only 224 days long. The earth comes next, being 91,430,000 miles from the sun. After this planet is Mars, 139,311,000 miles from the luminary. All astronomers admit that if people like those on the earth live on any of the other planets, Mars is probably the one. The reason why is easy to tell. Although Mars is further from the sun than the earth, his orbit is so eccentric that at certain times he is only 126,318,000 miles away; consequently, the temperatures are likely merely a little more moderate than those on the earth. Then, too, the diurnal motion of the two planets is about the same, so that from one year’s end to another the distance from the earth to Mars varies only from 33,800,000 miles to 61,800,000 miles. Mars has its seasons and. its polar ice just like the earth. Through the telescope we can watch icefields at the poles get larger as winter approaches, and see them get smaller again in the summer. Mars has an atmosphere and clouds like those on earth. There are continents and oceans on Mars, so that, altogether, the analogy between that planet and the earth is very close, the striking difference being that Mars is much the smaller. Astronomers are more and more disposed to believe that Mars is inhabited. You ask me if we know, however, and I promptly tell you we do not. An astronomer named Schiaparelli claims he is able to see a double line of canals on Mars. These must be enormous works if he can see them, and must represent a stupendous amount of work on the part of an almost countless number of people. I cannot see them through my telescope, and many others fail. After all, these canals may be in Schiaparelli’s eye. People get what is called astigmatism now a days, and see two pencils where there is only one. Perhaps that is what Schiaparelli has. But even if there are people on Mars, and even if they have built canals, as for talking with them ” (and the professor repeated the statement to make it more positive), “ as for talking with them, nonsense ! "—San Francisco Examiner.