SUN SPOTS AND THEIR EFFECTS. 665 



" concluded that the auroras observed in Europe and America exhibit a true 

 periodicity closely following the magnetic periods, but not perfectly iden- 

 tical with them ;" and Mr. Charles V. Walker, telegraphic superintendent 

 holds as an established fact that " earth currents, disturbed magnetometersj 

 and aurora, are parts of the same phenomenon." 



3. There is evidence of thermometric variations, or fluctuations of tem- 

 perature, in periods coinciding with the sun-spot cycles. The observations 

 in this case are, however, much comj)licated and obscured by the agency of 

 the atmosjDhere, which acts as a screen upon the earth's surface, disturbing 

 the radiations that would affect our thermometers. But a large number of 

 observers, among whom are Baxendell, Biandford, Stewart, Eoscoe, Piazzi 

 Smythe, Stone and Koppen, have accumulated numerous observations both 

 in the temperate zones and in the tropics, showing that " the calorific in- 

 tensity of the sun's rays is subject to periodical changes, the maxima and 

 minima of which correspond respectively with those of sun-spot frequency." 



4. The wind-disturbances of the earth's atmosphere follow the same law; 

 there being a coincidence between the frequency of cyclones and sun-spots. 

 Observations on other sides of the world, and in the tropics where the wind 

 disturbances are most violent, lead to the conclusion, as stated by Mr. Mel- 

 drum, that " the whole question of cj^clones is a question of solar activity ; 

 and that, if we write down in one column the number of cyclones in any 

 given year, there will be a strict relation between them — many sun-spots, 

 many hurricanes ; few sun-spots, few hurricanes." 



5. Confirmatory evidence of this is found in the records of shipping- 

 disasters. From the returns of marine casualties posted on Lloyd's loss 

 book it was found that they disclose " a cycle closely corresponding with 

 the sun-spot period. The percentage of casualties on the registered vessels 

 of the United Kingdom (Great Britain) was 17|^ per cent, greater during 

 the maximum two years in the common cycle than during the minimum 

 two years." 



6. It has been further shown bj' the observations of Baxendell, Meldrum, 

 Eawson,''Jelinck, Wex, Dawson, Hennessey, Broun, and Brockelsby, that 

 there is a fluctuation in the fall of rain in which the same law may be 

 traced ; that is, " a connection between the variations of the sun-spot area 

 and the annual rainfall; the rainfall rising above the mean when the sun- 

 spot area is in excess, and falling below the mean when in periods of 

 small sun-spots." The monsoons are the great sources of rain-supply at 

 Madras, in India'. The rainfall cycle has'been traced out in that country, 

 and the deficiency and excess of rain connected with the great solar peri- 

 odicities. The writers whom we are following- say, for example, that the 

 " water-supply brought to Madras by the southern monsoon is 26-^- per 

 cent, greater in ordinary years than in tlie years of minimum sun-spots." 

 And, again, '■ there is a rain-cycle of eleven j'cars at Madras which coin- 

 cides with the cycle of sun-spots; the periods of maxima and minima 

 in these two cycles di&elosing a remarkable coincidence." 



