Morning journal and courier., 1881-03-23
Sheffield Scientific School.

Close of the Mechanics' course-Lecture
 by Prof. Lyman on the Sun.
 Prof Lyman delivered the closing lecture in the Sheffield school annual course to me- chanics last evening, subject, ''The Sun" The very interesting lecture was heard with great interest by large audience which in cluded many prominent gentlemen.
 Professor Lyman apologized for changing the subject from the one announced, explain ing that the apparatus required was so small and the experiments so delicate that they He proposed therefore to speak of the 'sPresent State of our Knowledge of the Sum-
 The lecture was illustrated by the aid of spsctroscope.
 The lecturer spoke somewhat as follows:
 The sun is so evident source of light and life that is not surprising that it should early become an object of worship. In the very infancy of science the Greeks were taught by their philosophers that the sun was 8 mass of melted stone.
 Anaxagoras taught that the sun is in size as large as the Peloponnesus.
 It would be interesting to trace the history of opinions down to the beginnings of Gre clan science, when it was taught that the sun was twenty times larger than our earth, and so on to the era of telescopes. single lec- ture cannot cover the whole subject, hence it will be possible to speak only of the leading points.
 In the first place we must endeavor to gain some conception, however imperfect, of the suns magnitude. It seems only small disc, distant but a few rods or miles. When we speak of the sun being ninety-two millions of miles distant from the earth and as being S6O, GOO miles in diameter, we still have little idea of the vastness of these figures.
 If say that the sun is as much larger than the earth as a globe eighteen feet in diameter is larger than two inch ball, it will give some faint idea of the magnitude of the sun. The area of France or Spain represents the smallest area that can be seen with the aid of the most powerful telescope.
 At this point picture was projected upon the screen Illustrating the comparative size of the sun and the five largest planets. In the diagram the sun appeared to be about two feet in diameter, while the earth was about as large good sized pea.
 The main points of which the lecturer spoke were: 1st. Telescopic views of the sun.
 ?. Spectroscopic revelations concerning the sun.
 3. The corona.
 4. Some conclusions as to the consultation of the sun.
 Under the first division the Professor first spoke of the spots on the sun. A series of pictures were thrown upon the screen dis playing the general appearance of the spots on the suns disc.
 Comparing several successive observations of these spots it is noticeable that they change moving towards the East and disappearing from the suns disc, but reappearing again after an interval This movement is evi- | dently due to the suns rotation. From care- full and continued observations it has been that the time of the suns rotation l is about twenty-five days. But the time varies Even given point is observed to | vary in the time of it's rotation. From this I astronomers conclude that the sun | is in gaseous state.
 It has been observed further that the num- Der of these spots differ in different years. It | has been estimated that the period between | the maximum and minimum appearances is about eleven'years.
 A correspondence has been noted between the periodicity of the appearance of the suns spots and the periodical variation in the sarth's magnetism. Prof. Loomis, of this institution, has also discovered similar CO., incidence in regard 10 the periodicity of Au- roral displays. There were then shown @ number of illustrations of individual spots. The peculiar appearance of these was pointed put. The general opinion of astronomers s that these spots are Impressions on the ,urface of the sun. The depth of these de- oressions is unknown. If the light from the lark portion of the spot be admitted into the telescope through narrow aperture it is dis covered that the ttumbra" is not dark but ,nly less light than the surrounding.
 The whole surface of the sun has a sort of granular appearance. This appearance is described by some as like that of newly fallen lakes of snow upon the pavement, by others $ like that of grains of rice in soup. Twoj IT three views Illustrating this appearance were then shown.
 The Professor then described the princi- lies upon which the spectroscope depends l ray of sunlight conducted through pris- n gives 6 continuous band of light, upon 7hich are observed large number of black mes. These Tines are found to correspond Iith the colored bands which are produced v the light from various burning substances [ gases, e. g. sodium or hydrogen. In this lay it has been possible to learn much in re- ard to the composition of the sun. Many , { the substances with which we are familiar , ere are found to exist in gaseous state in he sun. But the revelations of the spectroscope are ct confined to the visible portion of the sun. has discovered to us glowing atmosphere .om five to ten thousand miles in height, en4l { eloping the sun. This is in constant agita- on. Several fine Illustrations of this ! were then displayed. There { re great diversities of form observable in ! lis. ! Of the Corona the Professor explained how