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280 This noticeable fact about the Pleiades is not very new. The late Mr. R. A. Proctor called attention to it forty or fifty years ago. But another group of stars in the constellation of the Bull was only noticed quite lately, by Mr. Lewis Boss, a great American astronomer. The movements of these stars are so slow—such a snail's "crawl"—that it required very great care and skill to measure them. The main point about the arrows in Fig. 91 (which again represent the movements in a given time about 50,000 years) is that they are not parallel to each other, but would meet in a point if carried far enough. It looks as though the stars would collide with one another at some time in the future, but that need not be the case. If you stand on the railway, where the lines run straight they will seem to meet in the distance, whereas we know that they always remain the same distance