SUN-SPOTS AND COMMERCIAL PANICS. 27 



as still sub judice. This, however, is only one relation out 

 of many now suggested. Displays of the aurora, being 

 unquestionably dependent on the magnetic condition of the 

 earth, would of course be associated with the sun spot 

 period, if the magnetic period is so ; and certainly the most 

 remarkable displays of the aurora in recent times have 

 occurred when the sun has shown many spots. Yet this of 

 itself proves nothing more than had been already known 

 namely, that the last few magnetic periods have nearly 

 synchronised with the last few sun-spot periods. It is 

 rather strange, too, that no auroras are mentioned in the 

 English records for 80 years preceding the aurora of 1716, 

 and in the records of the Paris Academy of Sciences one only 

 that of 1666, which occurred when sun-spots were fewest. 

 The great aurora of 1723, seen as far south as Bologna, also 

 occurred at the time of minimum solar activity. Here we 

 are not depending on either Wolf's period of 1 1 years or 

 Brown's of 10^ years ; from records of actual observation it 

 is known that in 1666 and 1713 there were no sun-spots. In 

 fact it is worth mentioning that Cassini, writing in 1671, says, 

 * It is now about 20 years since astronomers have seen any 

 considerable spots on the sun/ a circumstance which throws 

 grave doubt on the law of sun-spot periodicity itself. It is 

 at least certain that the interval from maximum spot-fre- 

 quency to maximum , or from minimum to minimum, has 

 sometimes fallen far short of 9 years, and has at others 

 exceeded 18 years. 



It appears again that certain meteorological phenomena 

 show a tendency, more or less marked, to run through a 

 ten-year cycle. Thus, from the records of rainfall kept at 

 Oxford it appears that more rain fell under west and south- 

 west winds when sun-spots were largest and most numerous 

 than under south and south-east winds, these last being the 

 more rainy winds when sun-spots were least in size and 

 fewest in number. This is a somewhat recondite relation, 

 and at least proves that earnest search has been made for 

 such cyclic relations as we are considering But this is not 



