In 1802 Dr. Wollaston, and later Fraunhofer, discovered and perfected an instrument called the spectroscope. It consists of a prism, fixed upon an iron stand, and a tube carrying a slit. When light passes through a slit it impinges upon a flint glass prism, by which it is dispersed. The light of burning metals has been tested in that manner. Thus when any light passes through the slit of a spectroscope, the substance giving the light may be determined, the elements burning ascertained. If the solar spectrum be examined--the light of the sun's rays--numerous dark lines parallel with the edge of the prism are observed, and reveal a number of colors giving the following: red, orange, yellow, green, blue, indigo, violet. These are intersected by fine black lines of different degrees of breadth and shade, which are always present, and always occupy the same relative position in the solar spectrum. These are called Fraunhofer's lines. By the means of this instrument, the spectra of the sun, planets, and moon have been analyzed, and the color and position, the kind of metals these distant bodies are composed of. The sun's atmosphere, from experiments made, is known to contain metals, such as soda, iron, etc., in the condition of glowing gas, the white light proceeding from the solid or liquid strongly heated mass of the sun which lies in the interior. The metals hitherto detected in the sun's atmosphere are about fifteen or more--iron, sodium, strontium, cadmium, magnesium, calcium, chromium, nickel, barium, zinc, cobalt, manganese, aluminium, titanium, hydrogen, etc. So delicate is this instrument that 1/180000000 part of a grain of sodium can be detected, and a portion of lithium weighing 1/6000000 part of a grain has been detected; thus showing that there exists a very strong probability that the sun, planets, and moons are composed of similar, if not the same, elements that this earth is composed of. CHAPTER IV. THE SUN. The Colossus, or brazen statue of the Sun, was placed across the mouth of the harbor of Rhodes, its legs stretched to such a distance that a large ship under sail might easily pass between them. It was seventy cubits high, or a hundred English feet; its fingers were as long as ordinary statues, and few men with both arms could grasp one of its thumbs. Scarcely sixty years had elapsed before this work of art was thrown down by an earthquake, which broke it off at the knees, in which position it remained till the conquest of Rhodes by the Saracens (A.D. 684), when it was beaten to pieces and sold to a Jew merchant, who loaded nine hundred camels with its spoils.