58. Q. What are some of the materials composing the cromosphere? A. Hydrogen is the principal material of its upper part; iron, magnesium, and other metals, some of them as yet unknown on earth, in the denser parts below.
59. Q. When only are the corona and cromosphere visible? A. Only during total eclipses, or by the aid of the spectroscope.
60. Q. What is all that we ordinarily see with the eye or telescope of the sun? A. The shining surface called the photosphere on which the cromosphere rests.
61. Q. What is the diameter of the photosphere, or the visible and measurable part of the sun? A. Eight hundred and sixty thousand miles.
62. Q. How many globes like the earth would it require to measure the sun’s diameter? A. One hundred and eight.
63. Q. What is the volume of the sun as compared with that of the earth? A. It is 1,245,000 times greater.
64. Q. What is the density of the sun as compared with that of the earth? A. It is only one-fourth as great.
65. Q. What is the mass of the sun as compared with that of all the planets, asteroids, and satellites of the solar system put together? A. It is seven hundred times as great.
66. Q. What are some of the opinions as to the surface of the sun? A. That it is hot beyond all estimate is indubitable. Whether it is solid or gaseous we are not sure.
67. Q. What on the surface of the sun have been objects of earnest and almost hourly study on the part of eminent astronomers for years? A. The spots.