been observed." Nor was this all. A magnetic storm never rages without various signs of electrical disturbance. On this occasion vivid auroras were seen, not only in both hemispheres, but in latitudes where auroras are very seldom witnessed. They were conspicuous, on the nights following this observation, in Cuba, Rome, South America, and Australia—at Melbourne greater than was ever witnessed there before. Sir John Herschel says:
The establishment of so important a fact as the periodicity of the phenomenon of solar spots, and a corresponding periodicity in the action of one of the most subtle of the terrestrial forces, was an event of great moment in the scientific world. For, as the physical forces are correlated and convertible, if any one of them be implicated there arises the presumption that others also may be involved, and a new branch of inquiry is thus opened. Wolf, of Zurich, impressed by the import of the case, addressed himself to the Herculean task of exploring the whole history of past observations of the sun-spots. He overhauled the unknown and forgotten records of old observations, collating the results found in some eleven hundred volumes of print and manuscript, and consulting double that number, which did not pay for the trouble of unearthing them from the dust in which they were buried. His data enable him to give the annual course of the phenomena of spots from 1750 to 1860, that is, for more than a hundred years. For one-half of that time he can make a monthly statement; and is able to trace the maxima and minima with sufficient exactness during the past 140 years. The data procured by Prof. Wolf in this protracted investigation comprehended observations in the seventeenth century on 2,113 days; in the eighteenth century on 5,490 days; in the nineteenth century on 14,860 days, or a total of 22,463 days. The old observers little suspected the ultimate meanings that were to be drawn from what they were doing. But in science nothing is lost; observations at first thought trivial, become at length significant, and serve to establish the most comprehensive views.
It follows from these discoveries that, in the system of the universe, there is reason to rank the sun with the variable stars. How far the phenomena of his spots are linked with planetary influences, is an interesting question to which astronomers are directing their attention. They are also investigating the relations of the sun's spots to the temperature of the earth, and other terrestrial conditions, with results which we have no space left to consider.
