158 THE POPULAR SCIENCE MONTHLY. 



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 : 



"These auroras were accompanied with unusually great electro-magnetic 

 disturbances in every part of the world. In many places, the telegraphic wires 

 struck work. They had too many private messages of their own to convey. 

 At Washington and Philadelphia, in America, the telegraphic signal-men re- 

 ceived severe electric shocks. At a station in Norway, the telegraphic appara- 

 tus was set fire to ; and at Boston, in North America, a flame of fire followed 

 the pen of Bain's electric telegraph." 



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 1*750 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 uni- 

 verse, 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 atten- 

 tion. 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. 



