Page:Popular Science Monthly Volume 20.djvu/315

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soon as they learned the Dippers in Ursa Major and Ursa Minor, and Cassiopeia, I put them to making observations at an interval of several hours on the same night, so as to find out the daily apparent motion. Thus far they knew Polaris only as "the star in the handle of the Little Dipper." It was some days before all reported observation, and I did not indorse any report until we had full concurrent testimony that from 6 p. m. to 12 the Great Dipper moved down toward the horizon and then east (it was autumn), that Cassiopeia moved up and then west, and that the bowl of the Little Dipper had turned on the handle until it was nearly upside down. They drew the Little Dipper on the blackboard, and made arrows to indicate the direction in which the other constellations moved. They remarked, without prompting, that the arrows made a kind of circle. After another night's observation, the report was brought that at 6 p. m. the constellations had returned to the positions occupied by them at 6 p. m. of the previous day. They said the stars must have gone entirely round that star in the handle of the Dipper, or else have moved backward. By this time the interest had become so great that a number of girls rose before day to take a look; so we had a further report. When they had settled as fully as they could the fact of the apparent motion, I asked them, "When an object seems to move, does it always prove to be in motion? "Many cited in answer the apparent motion of the trees when one journeys by rail. After drawing from them the fact that the real and the apparent motions are always in opposite directions, I asked, "Do you think the earth is turning round, or are the stars moving round it? "Up to this time several intelligent girls had been without suspicion that they were coming round to the familiar fact of the earth's rotation on its axis, learned from the beginning of their geographies. Their surprise, when my question flashed this result on them, was very amusing. It was to me a striking illustration of the inadequacy of learning things about nature from books alone.

I will not weary the reader with an account of the observations which detected the apparent annual motion of the stars, and the facts and questions which led them to conclude that it resulted from a real motion of the earth, in a circle, with the sun in the center. They also detected the apparent motion of the sun north and south, and had a very interesting discussion whether this was real or apparent. In the course of this study, they experimented in a darkened room with a light, and a ball revolving on its axis. The ball was held at the solstitial and equinoctial positions, and revolved, and they drew the conclusions regarding length of days. The work was just as much as possible their own.

One of the most interesting studies made by my pupils was that of the moon. They began with the new moon, and of course very soon accounted for its daily apparent motion west, Then they watched the real motion from night to night. I must not forget to say that regu-