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128 To further appreciate this apparent change in the situation of the constellations, the student should refer to the large plates successively. In each successive one he will note the advancement westward of the constellations mentioned above, rising in the east late at night.

The student can best get an idea of this westward apparent movement of the stars by noting the position of some bright first-magnitude star from night to night. He will soon be able to calculate the position of this star a month or more ahead, and this calculation applies to all the constellations and stars.

It is not within the scope of this work to go into this matter in detail. The author merely desires to mention this fact of apparent change of position in the stars, a fact that will be noticeable to the observer in a short time, and a fact that it is hoped he will be able to explain to his own satisfaction with the aid of the foregoing remarks.

It will be noticed that the stars on the diagrams are all numbered and lettered. The numbers refer to the magnitude of the star,—that is, the brightness of it, the first-magnitude stars being the brightest, the second-magnitude stars less bright, etc.

The letters are those of the Greek alphabet, and the student if not familiar with it is advised to consult a Greek grammar.

In the text, in referring to certain stars in the