SUN SPOTS AND THEIR EFFECTS. 663 



compartment upward, two griffins facing one another, and in the upper- 

 most compartment two eagles. It can not be doubted that this, the first 

 discovery of its kind made at Olympia, is destined to furnish an invaluable 

 link in the study — for which the materials are only now beginning to be 

 collected and compared — of the origins of the Greek art. — Academy. 



ASTRONOMY. 



SUN SPOTS AND THEIR EFFECTS. 



The phenomena of sun spots are now familiar : multitudes of people 

 have seen them, and everybody has read about them. It is well known that 

 the surface of the sun is not that uniform disk of light that it was formerly 

 supposed to bo, but abounds in gulfs, dark chasms, up-rushing streams of 

 flaming gases, and lurid prominences, sometimes 100,000 miles high. But 

 these striking effects are not uniform : the sea of solar fire like our two 

 oceans, is sometimes violently agitated and sometimes quiet. The spots are 

 variable, being now many and enormous in size, and again few and small. 

 This periodicity, moreover, is proved to be regular. Prof. Schwabe, of 

 Dessau, discovered that, instead of being uniform in number and intensity 

 from year to year, spots increase and decline at definite rates for a term of 

 years. As a result of 9,000 observations, during which he discovered 4,700 

 groups, he traced three complete oscillations from maximum to minimum, 

 which he estimated to take place in about ten years. Prof. Wolf, of Zurich, 

 went into an exhaustive history of the subject, and by collating avast num- 

 ber of observations and records from 1750 to 1860, h© verified Schwabe's 

 general results, but showed that the period of oscillation is about eleven 

 years. His data, scattered through a course of 140 years, comprehended 

 observations in the seventeenth century made on 2,113 days ; in the eight- 

 eenth century, on 5,500 days ; and in the nineteenth century, on 14,860, or 

 a total of 22,463 days. On this broad basis of observation, made with no 

 reference to any hypothesis 6f variation, it is established that the solar 

 energy changes in intensity by a regular law of rise and fall from a maxi- 

 mum to a minimum of effect ; and that the maximum, or greatest activity, 

 coincides with the period of violent perturbation when there is the greatest 

 number of eruptions of heated matter j^from below, and the most conspicu- 

 ous display of sun-spots and prominences ; while at the minimum periods 

 these manifestations are greatly reduced, or almost entirely wanting. 



It is now an admitted fact of science that the earth is dependent upon the 

 sun for the chief portion of the energy by which terrestrial effects are pro* 

 duced. With the exception of the ebb and flow of the tides, all the forms 



