METEOROLOGY AND ALLIED SUBJECTS. -327 



earlier than the eastern; he also shows (2d) that extensive famines in 

 India accompany or directly follow a maxima of pressure. 



Balfour Stewart concludes that the sun's heat is most effective dur- 

 ing a maximum of sun spots. Mr. Eaton has collected barometric 

 records for a hundred years at London, and Archibald has shown that 

 these give some little evidence of the same sun spot periodicity as in 

 India, namely, a maximum of spots corresponding to a minimum of pres- 

 sure. The reverse holds good for St. Petersburg. • [Z. 0. 0. M., XVI, 

 1881, p. 158.) 



Koppeu has continued his classical researches on secular perfods in 

 the weather, by extending his studies of annual mean temperatures to 

 cover all recent data, for the years 1841 to 1875, published since the 

 publication of his previous memoir. The resulting curves as given by 

 Koppen show the mean temperature for the north temperate, the tropi- 

 cal, and south temi^erate zones, as well as the curve of sun-spot fre- 

 quency, and lead to the following remarks : The curve for the southern 

 hemisphere shows both a general agreement with the spot curve, and 

 also a series of special systematic discrepancies. If we were not, accord- 

 ing to our experience in the northern hemisphere, to entertain a decided 

 mistrust of generalizations based on only three sun spot periods, then 

 we might also detect a decided law in these discrepancies in the southern 

 hemisphere. We see, namely, that while the sun-spots increase the 

 temperature, curves in all the three zones describe the double wave 

 in the years 1843 to 1856, the first valley in this double wave, but in 

 the two following periods the second vaUeys, all preceding the S])ot 

 minimum by from two to four years, give in each case the absolute 

 minima of temperature. In the northern hemisphere the remarkable 

 agreement of the curves for temperature and spots from 1820 to 1840 is 

 gradually disturbed, and after 1852 entirely disappears, although the 

 temperatures from 1867 to 1869 give indications of a return of earlier 

 laws. The gradual rise of the temperature in the northern hemisphere 

 for 1875 to 1878 is again in good agreement with the simultaneous di- 

 minution of the number of spots, but the succeeding abnormally cold 

 year in Europe forces vividly upon the attention the care that must 

 be exercised when one \7ould use for purposes of prediction an ap- 

 parent law whose rationale is as yet not understood, and to which is 

 subject to mysterious, and therefore wholly unexpected, disturbances. 

 {Z. 0. 0. If., XVI, 1881, p. 149.) 



Blanford, in some further remarks on sun-spot cycles, states that out 

 of the investigations of Gautier, Stone, Koppen, and others, it results 

 that the variation of temperature at tropical stations during the sun- 

 spot cycles is such that the highest temperatures occur nearly always 

 with the minimum of spots. The intensity of the solar radiation accord- 

 ing to the results obtained by Baxendall, and those obtained by me 

 from ten Stations in India, attains its maximum simultaneously with 

 the spot maximum. The variations of atmospheric pressure at stations 



