EDITORIAL NOTE V 



Others there is an absence of explanation. This difference could not 

 be corrected without unduly delaying the publication of the data. 



In general an effort was made by the compilers of the data to reduce 

 the monthly and annual means to a uniform comparable series, in so 

 far as the hours of observation and the height of the barometer were 

 concerned. 



The totals of precipitation are understood to include all forms of 

 condensed moisture ; as rain, snow, sleet, hail, dew, frost, etc. The 

 snow, sleet, hail, frost are given in their equivalents of water by melt- 

 ing, weighing or estimating. In the tropics, the precipitation is chiefiy 

 rainfall, in temperate latitudes it is rain and snow, and in the polar 

 regions chiefly snow. 



For many of the stations averages of the series, or normals, were 

 given by the compilers. For others they were computed by the writer. 



Because relations between meteorological conditions and solar 

 changes are frequently a su1)ject of research, an appendix is added 

 to the volume giving the relative sun-spot numbers of Wolf and 

 Wolfer as revised by Dr. A. Wolfer of Zurich. Huntington,' Clay- 

 ton,^ and Bauer ^ have all independently found an annual period in 

 these numbers, the results of which are given below in percentages 

 of the mean value: 



Jan. Feb. Mar. Apr. May Juno July Aug. Sept. Got. Nov. Dec. 



Hunt. 98.8 99.5 99.7 100.0 101.5 101.4 100.1 99.8 100.4 101.0 101.0 99.7 

 Clay. 93.6 92.5 103.4 103.6 100.2 99.1 100.4 103.0 103.2 102.0 99.1 98.6 

 Bauer 87.8 97.1 112.0 89.8 103.2 116.1 114.5 110.2 97.8 90.7 90.5 91.8 



Mean Dkpartuhes from Annual Mhan — Bauek and Clayton. 



Jan. Feb. Mar. Apr. May June July .\ug. Sept. Oct. Nov. Dec. 

 Obs. —9.3 —5.2 +7.7 —3.3 +1.7 +7.6 +7.5 +6.6 +0.5 —3.6 —5.2 —4.8 



Comp. -6.4 —4.7 —1.8 +1.8 +4.7 +6.4 +6.4 +4.7 +1.8 —1.8 —4.7 —6.4 



The mean departures of the results of Bauer and Clayton from 

 the annual mean are given above. When these are subjected to 

 harmonic analysis they show an amplitude of 6.6 per cent with epoch 

 about April i. The computed values for each month are given below 



'"Earth and Sun," by ICllsworth H;intiiigton, New Haven, 1923, p. 249. The 



2b 



4 



results given here are smoothed hy the fornuila "■" ~ ' - . The means are for 



the years 1749-1913. 



^ " Earth and Sun," loc. cit., p. 229, chapter by H. H. Clayton. The means are 

 for the interval 1856-1912. 



'"Studies Concerning the Relations Itetween tlic Activity of the Sun and of 

 the Earth's Magnetism," by Louis A. Kauer and C. R. l^uval, 'I'crrc's. Magnet, 

 and Almos. Elec, l)ec. 1925. The means are for tlie interval 1913-1922. 



