418 Bigeloio — Meteorological Elements of the United States. 



Table III. — The Amplitude of the Horizontal Magnetic Force without regard to sign. 



Tear 



Jan. 



Feb. 



Men. 



Apr. 



May 



June 



July 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. H M 



H-M 



1872 



186 



217 



235 



220 



260 



208 



228 



265 



192 



275 



252 



174 2712 2033+679 



1873 



206 



145 



186 



178 



146 



157 



105 



141 



94 



152 



140 



1531803 2054—251 



1874 



146 



262 



195 



250 



149 



160 



162 



146 



124 



203 



137 



128,2062 1894J + 16S 



1875 



110 



195 



168 



142 



133 



142 



106 



94 



139 



126 



111 



103! 1569 1630 - 61 



1876 



119 



128 



154 



93 



105 



75 



82 



98 



106 



75 



127 



161jl323 t 168l|-358 



1877 



125 



84 



100 



85 



142 



128 



153 



145 



89 



98 



144 



102 1395 1715 -320 



1878 



178 



157 



168 



161 



170 



241 



151 



140 



154 



144 



227 



167 2058 1948, +110 



1879 



241 



129 



138 



123 



189 



224 



183 



173 



194 



220 



177 



242 2233 2250!- 23 



1880 



188 



169 



195 



138 



297 



176 



166 



380 



268 



305 



235 



213,27302729'+ 1 



1881 



250 



371 



198 



212 



161 



239 



265 



181 



303 



189 



252 



24512866 2946 j— 80 



1882 



206 



193 



252 



458 



242 



350 



148 



311 



244 



359 



577 



317 3757l3144 l + 613 



1883 



197 



297 



245 



323 



215 



231 



255 



242 



353 



241 



331 



216 3146 3193 - 47 



1884 



259 



250 



263 



266 



248 



283 



257 



289 



273 



234 



319 



282 



3223 3204!+ 19 



1885 



330 



227 



251 



200 



383 



246 



214 



199 



256 



207 



229 



240 



2973 2920!+ 53 



1886 



275 



15b 



308 



272 



242 



187 



220 



205 



315 



304 



263 



171 



2920j2779j+142 



1887 



182 



159 



183 



184 



172 



154 



202 



244 



255 



171 



234 



196 233612569-233 



1888 



228 



155 



258 



228 



244 



183 



170 



179. 



182 



220 



219 



176 2432 2298+144 



1889 



152 



119 



165 



164 



153 



149 



188 



152 



245 



222 



305 



158;2172 2220 '.— 48 



1890 



129 



125 



137 



101 



99 



134 



149 



139 



143 



179 



157 



1271619 2473-854 



1891 



155 



185 



195 



219 



291 



142 



208 



181 



330 



186 



212 



227 25312613 - 82 



1892 



250 



286 



387 



374 



378 



324 



358 



282 



224 



230 



257 



249|3599;2795!+804 



1893 



170 



320 



266 



184 



242 



263 



267 



342 



249 



283 



299 



2593144 2993+151 



1894 



186 



361 



324 



237 



217 



187 



286 



318 



283 



156 



310 



215 3080 3073 + 7 



1895 



180 



198 



175 



217 



251 



178 



187 



243 



232 



303 



249 



198 261l|2806 — 195 



1896 



255 



189 



232 



192 



323 



280 



218 



203 



259 



221 



292 



266J2930 2650 +280 



1897 



261 



179 



195 



215 



221 



218 



206 



129 



129 



138 



119 



254 2264:2441—177 



1898 



198 



212 



249 



229 



185 



206 



130 



145 



246 



240 



154 



172 2366i2236|+130 



1899 



162 



196 



223 



235 



201 



169 



159 



136 



146 



112 



159 



134|2032jl925!+107 



1900 



115 



107 



235 



175 



193 



95 



93 



132 



80 



133 



113 



11811589 1785 —176 



1901 



107 



139 



160 



83 



103 



112 



111 



96 



122 



100 



90 



151 1374 1717 -348 



1902 



117 



79 



109 



145 



169 



112 



112 



94 



83 



163 



177 



103:1464:1853 -389 



1903 



82 



98 



117 



197 



94 



96 



132 



162 



124 



321 



454 



249212611896+230 



1904 



191 



130 



93 



169 



172 



207 



148 



119 



125 



153 



181 



991787 



2000 -213 



1905 



139 



216 



271 



207 



159 

 201 



107 

 203 



164 



189 



151 



205 



198 



118 



290 



176 2194 



2180 



+ 14 



Means 



185 



189 



184 



191 



199 



199 



229 



189 









the table shows the average number of days on which obser- 

 vations were made, 13 in the midwinter and 26 in the mid- 

 summer, while the line above shows the average number of 

 prominences seen on the edge of the sun's disk per day in each 

 month. It will be noted that there is a small semi-annual 

 period in these day-numbers, which will be considered in a 

 later section of this paper. 



It was found the most simple, and approximately sufficient, 

 method to use the variations of the horizontal magnetic force 

 in the European field, though strictly the total disturbing vec- 

 tor for the entire hemisphere should be carefully computed. 

 Practically, the horizontal force at from three or four stations, 

 Pawlowsk, Pola, Paris, Greenwich, were plotted on diagram 

 paper month by month, and mean lines were drawn to elimi- 



