Advertisement

Professor Searle's Lecture.

Last night Professor Searle delivered the second lecture in his series on Astronomy, the subject being "The Sun."

Every one has noticed the apparent north and south motion of the sun among the sun among the stars, from north in the summer to south in the winter.

Further, it has been discovered that the sun has a slower apparent diurnal motion than the stars; that is, the sun, and a star rising at the same time, the star would set before the sun. Careful measurements show that this difference in fine is about four minutes. The motions of the sun and stars differ in direction as well as in speed. The sun apparently moves in a great circle, a circle at the centre of which the observer seems to stand. While the courses of the stars are small circles. This great circle which the sun describes is called the ecliptic.

Professor Searle went on to describe the motion of the moon with the reference to the earth and sun, and so came to the subject of eclipses. Eclipses of the sun, though generally partial, are sometimes total. In such cases the bright light which is visible around the sun is called the corona, and is supposed to be due to the reflection of light from floating particles in the sun's atmosphere. This, however, is only one of several theories about the matter. In a total eclipse, too, we notice certain red spots around the edge of the moon, and for a long time was a disputed question whether these spots belonged to the moon or to the sun. They were called protuberances, and the spectroscope finally showed that they were a part of the surface of the sun.

The consistency of the sun has never been determined. At present the theory is that it consists of gaseous matter intensely heated. Under this theory, the so called "sun spots" are supposed to be places which are for unknown reasons comparatively cool.

Advertisement