Wishing to show a friend the extraordinary sight of a Brocken Spectre, I took him up the hill on a misty day like that which has been briefly described. According to surmise, two spectres appeared instead of one, but the halo was not doubled as well as the shadow. I could see my friend’s shadow, and he could see mine. But, although the halo was as bright as before, each of us could only see it encircling his own head. We stood as close to each other as we could, we moved apart as far as the nearly conical top of the hill would allow, and in both cases each of us could only see his own halo. Perhaps the reader may remember the wonderful spectre-scene drawn by Mr. Whymper, and viewed from the Matterhorn just after the accident which had killed several of his companions in the ascent of the hitherto impregnable peak. In the mist there suddenly appeared three vast dark crosses enclosed in an oval. Considering the highly-strung nerves of the survivors, it was no wonder that they were all shaken by such an appearance, and that the guides were for a time too frightened to proceed. THE SPECTROSCOPE. Next we come to one of the most astonishing and beautiful optical instruments ever made by the hand of man. It is called the Spectroscope, because it deals with a certain arrangement of rays which is called a “spectrum.” Many years ago Newton discovered the cause of the lovely colours which deck the rainbow, and the fact that, by passing a ray of white light through a prism, it was decomposed into seven colours, which invariably came in the following order--Red, Orange, Yellow, Green, Blue, Indigo, and Violet. He also discovered that, by looking at that coloured band through another prism arranged in a different manner, the decomposed rays were again brought together, and white light was the result. Newton had thrown the light on the prism through a round hole, but some time afterwards Dr. Wollaston employed a narrow slit for the purpose, and then found that the spectrum was traversed by dark lines which never changed their places. On these lines depend all the discoveries that have been made by the aid of the Spectroscope. The chief of them are designated by the letters of the alphabet. (See page 300.) It was soon found out that if burning gases were viewed with the Spectroscope, lines were still seen, but they were bright instead of dark, and that they invariably occupied the place of one or more of the dark lines shown by the spectrum of sunlight. Then it was discovered that these burning gases absorbed or stopped out the light in the solar spectrum, and from that moment the science rapidly advanced. At the present day the Spectroscope not only determines the metals which exist in the sun, but also those of the fixed stars. It even analyzes the constitution of double stars, and shows the reason why one star should be red and the other green. One of the most astonishing discoveries in astronomy was due to the Spectroscope.