80 A! NL'AL RECORD OF SCIENCE AND INDUSTRY. 



and Zwanenburg, for the years 1690 to 1784, and finds that, 

 from 1723 to 1766, each minimum of sun-spots corresponds 

 to a less rain-fall than the preceding, and following sun-spots 

 maxima; but that, on the other hand, before 1723 and after 

 1 766, the reverse takes place. Astron. Maeh., LXXXIIL, 286. 



SOLAR SPOTS AND TERRESTRIAL PHENOMENA. 



The last number of the Astronomical Notices of Dr. Wolf 

 contains a valuable contribution by him to the literature of 

 the solar spots and their relation to terrestrial phenomena. 

 As is well known, Wolf's previous studies on this subject 

 have been the starting-point of nearly all the most recent in- 

 vestigations that have been made; and, indeed, his series of 

 numbers representing the relative spot area of the sun's sur- 

 face during the past 200 years is the standard authority re- 

 lating to that subject. The present communication begins 

 with the consideration of the subject of the relation between 

 magnetic variation and the frequency of sun-spots; and the 

 author first of all prepares a table showing the magnetic va- 

 riation, in Europe, for over 100 years, founding his studies 

 upon long series of observations made at eight stations. The 

 magnetic variation at each station is represented by a form- 

 ula so satisfactory that Wolf concludes that the simultaneous 

 variations at different places vary among themselves, princi- 

 pally, by a constant quantity, and the influence of the sun- 

 spots is nearly the same for each series. Hence he is justi- 

 fied in considering all these eight stations as representing, in 

 general, the magnetic condition over Europe. The mean of 

 the separate results belongs, therefore, to a station in the 

 midst of the eight stations. As a central normal station, 

 Wolf chooses the city of Prague, for which the longest series 

 of observations is at hand. He is then able to find a normal 

 variation, which may be considered to be, to a great extent, 

 freed from the influence of local peculiarities. When the 

 spot phenomena are irregular, so also are the variations ; 

 when they increase or diminish, the magnetic variations do 

 so likewise. In his last communication on the solar spots, 

 Wolf states that in 1852 he showed, from a review of eio;ht 

 centuries of weather notes in the older chronicles of Switzer- 

 land, that the years rich in sun-spots are, in general, drier 

 and more fruitful than those that are poor in sun-spots, the 



