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THE POPULAR SCIENCE MONTHLY 



nections that have been disclosed be- 

 tween the variations of solar activity 

 and resulting terrestrial phenomena : 



1. The first coincidence observed 

 was in the field of terrestrial magnet- 

 ism. "A freely-suspended magnet, al- 

 though it points in one direction, is 

 nevertheless, within small limits, al- 

 ways in motion. Certain of these mo- 

 tions depend, as is well known, upon 

 the hour of the day; but the magnet 

 is also liable to irregular, abrupt fluc- 

 tuations, which cannot be connected 

 with the diurnal oscillations. While 

 Hofrath Schwabe was engaged in de- 

 lineating the sun-spots, Sir Edward 

 Sabine was conducting a series of ob- 

 servations with regard to these spas- 

 modic affections of the needle, and he 

 found that such fluctuations are most 

 frequent in years of high sun-spot ac- 

 tivity." Nearly a hundred years ago, 

 Van Svvinden had suggested a perio- 

 dicity in these irregular magnetic move- 

 ments. Gauss, Arago, Lamont, and 

 Gautier, pursued the research, and es- 

 tablished the existence of a cycle of 

 magnetic variation having an eleven- 

 year period, the maxima and minima 

 agreeing with the maxima and minima 

 of sun-spot activity. Schiaparelli and 

 Broun have confirmed these results, 

 and the latter observer concludes that, 

 while the sun-spot activity is not an ex- 

 act measure of magnetic action, "each 

 is a distinct result due to the same 

 cause. 11 This disturbance is so great 

 that, in years of maximum sun-spots, 

 the working of the telegraph has been 

 powerfully interfered with. 



2. Connected with these effects there 

 have been observed corresponding dis- 

 turbances of electrical activity. A mag- 

 netic storm never rages without vari- 

 ous accompanying signs of electrical 

 excitement. These are seen in auroral 

 displays that in their varying intensi- 

 ties conform to the magnetic cycles. 

 Prof. Loomis, of Yale College, after a 

 critical study of the subject, " concluded 

 that the auroras observed in Europe 



and America exhibit a true periodicity 

 closely following the magnetic periods, 

 but not perfectly identical with them ; " 

 and Mr. Charles V. Walker, telegraphic 

 superintendent, holds as an established 

 fact that " earth - currents, disturbed 

 magnetometers, and aurora, are parts 

 of the same phenomenon. 11 



3. There is evidence of therm ometric 

 variations, or fluctuations of tempera- 

 ture, in periods coinciding with the sun- 

 spot cycles. The observations in this 

 case are, however, much complicated 

 and obscured by the agency of the at- 

 mosphere, which acts as a screen upon 

 the earths surface, disturbing the radia- 

 tions that would affect our thermome- 

 ters. But a large number of observers, 

 among whom are Baxendell, Bland- 

 ford, Stewart, Eoscoe, Piazzi Smyth, 

 Stone, and Koppen, have accumulated 

 numerous observations both in the tem- 

 perate zones and in the tropics, showing 

 that " the calorific intensity of the sun's 

 rays is subject to periodical changes, 

 the maxima and minima of which cor- 

 respond 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 opposite sides of the 

 world, and in the tropics where wind- 

 disturbances are most violent, lead to 

 the conclusion, as stated by Mr. Mel- 

 drum, that " the whole question of cy- 

 clones is a question of solar activity ; 

 and that, if we write down in one col- 

 umn the number of cyclones in any 

 given year, there will be a strict rela- 

 tion between them many sun spots, 

 many hurricanes; few sun-spots, few 

 hurricanes." 



5. Confirmatory evidence of this is 

 found in the records of shipping-disas- 

 ters. From the returns of marine casu- 

 alties posted on Lloyd's loss-book it was 

 found that they disclose " a cycle close- 

 ly corresponding with the sun-spot pe- 

 riod. The percentage of casualties on 



