A NEW SOLAR THEORY. l7l 



The theory also accoqjits satisfactorily for the existence of a "great" 

 period of solar phenouiena. , This greater cycle is brought about by 

 the influence of the • surface fluctuations of temperature described 

 above on the intensity of the convection currents which regulate the 

 interchange of ht^at between the intmior and the surface. It is incon- 

 ceival)le that in a gaseous body lik(» the sun, governed ))y a gigantic 

 convection, changes o-f temperature of parts of its mass can be con- 

 hned merely to the surface. Hence we nuist conclude that the distri- 

 bution of temperature throughout a considei'able part of the sun's 

 bulk will l)e more or less affected l)y the fluctuations of temperature 

 at the surface, and that, consequently, the intensity of the S3\stem of 

 convection currents, which depend on this distribution of temperature, 

 must undergo variations similar to those exhibited l)y the dynamical 

 phenomena at the surface. Now these variations must react on the 

 development of eruptions and spots. If the currents are weak — viz, 

 if the transfer of heat from the interior to the surface^ is comparatively 

 small — the cooling of the atmosphere must proceed ra})idly, and hence 

 the development of eruptions, which are a direct consequence of this 

 process of cooling, nmst lie energetic. At such times w^e have, there- 

 fore, to expect solar c3a'les with a powerfiil display of dynamical phe- 

 nomena. If, on the otlier hand, the currents are intense — viz, if the 

 heat supply from the interior is vigorous — the rate of atmospheric 

 cooling will be small, and we have then to expect cycles with only a 

 weak development of surface phenomena. 



Since the quantity ^r depends on the rate of cooling of the atmos- 

 pheric la3a^rs, it will attain high values at times when the spot develop- 

 ment is powerful, and vice Aersa. Now, the greater (v the greater will 

 be the dift'erence Ix^tween A^" and A.^-, and, conse({uently. the earlier 

 must the time of maximum, ?',^,, occur. Hence the position of the max- 

 imum in the spot period relatively to the preceding miniuium must 

 depend on the greater or less vigor of spot development during the 

 cycle, inasmuch as the time of maxinnun nuist be the more in advance 

 of the center of the period the greater the disph\y of tlie dynamical 

 phenomena. This important conclusion, arrived at by purel>" theoret- 

 ical considerations, is amply corro))orated ])y the facts. I refer in 

 this respect to a recent pul)lication of Dr. W. Lockyer, in which this 

 peculiar shift of the maximum is pointed out as a feature of the 

 olxserved spot curves. 



Professor Wolfer. of Zurich, in the Monthly Weather lieview of 

 April. 19(l!^. has also veriticd this peculiar th(M)retical I'csult l)y a 

 thorough discussion of the sun-spot observations from 174i> to liM)l. 

 "Only one result,'*' he says, "which Dr. Lockyei- has bi-ought out is 

 certain, and one which was also (((Muoiistrated by Dr. Halm, both from 

 the ohsei'ved facts and as a c()nse(iuen(;e of his now theory of the 

 periodicit}" of the solar phenomena, namel}', '^^ * * that a maximum 



