The remarkable connexion which has been observed between the changes in the physical condition of the surface of the sun and terrestrial phenomena, must not escape our notice. Sir William Herschel thought he perceived a link connecting the dark spots on the sun’s face with the variations of the earth’s temperature. This has not, however, been confirmed by the observations which have been made since the time of Herschel. The careful examinations of the solar spots which have been made by Schwabe,[175] prove a well-defined order of progress in them. He has discovered that they move in cycles of ten years--from the smallest number visible in a given year, they regularly increase for five years, when they reach their maximum; they then as regularly decrease, and at the end of another five years they are at their maximum number. The magnetic observations which have been carried on by the British and other governments for some years, over every part of the world, have elicited the fact that the order of variation in the earth’s magnetic intensity is in cycles of ten years, and the law of increase and decrease which is found to prevail with the solar spots distinctly marks the variations of terrestrial magnetism. Few more interesting facts than this are within the range of our knowledge, proving as it does the direct dependence of terrestrial phenomena on solar force. The constancy with which a magnetised needle points along a certain line which varies a little from the earth’s axial line, renders it one of the most important instruments to the practical and the scientific man. The wanderer of the ocean or of the desert is enabled, without fear of error, to pursue his path, and in unknown regions to determine the azimuth of objects. The miner or the surveyor finds in the magnetic compass the surest guide in his labours, and the experiment is for ever studying its indications. “True as the needle to the pole,”