470 



DISCUSSION OF BAROMETEIC OBSERVATIONS. 



mean of the departures of the daily means from the normal value." The 

 series of the mean departures thus obtained is as follows, in thousands 

 of an inch of mercury : 



Table V. 

 Means of the Departures of Daily Means from Normal Value. 



Day of the month. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 .* 



17 



18 



19 



20 



21 



22 



23 



24 



25 



26 



27 



28 



29 



30 



31 



Sums 



Means 



235 

 232 

 214 

 174 

 190 

 225 

 234 

 291 

 222 

 342 

 184 

 183 

 239 

 240 

 233 

 192 

 227 

 223 

 255 

 171 

 240 

 239 

 229 

 255 

 240 

 242 

 197 

 186 

 190 

 270 

 178 



219 

 253 

 208 

 296 

 257 

 195 

 23G 

 249 

 260 

 197 

 209 

 229 

 143 

 179 

 201 

 265 

 263 

 237 

 190 

 196 

 223 

 197 

 234 

 251 

 296 

 183 

 213 

 248 

 192 



214 

 251 



180 

 187 

 205 

 234 

 173 

 223 

 208 

 195 

 197 

 167 

 207 

 161 

 166 

 251 

 224 

 167 

 234 

 157 

 260 

 211 

 221 

 249 

 247 

 203 

 166 

 209 

 226 

 233 

 250 



294 

 224 

 178 

 231 

 222 

 202 

 175 

 169 

 171 

 159 

 135 

 172 

 190 

 230 

 166 

 226 

 197 

 163 

 185 

 162 

 177 

 152 

 176 

 186 

 177 

 190 

 136 

 161 

 172 

 180 



171 

 179 

 191 

 151 

 133 

 142 

 152 

 179 

 145 

 131 

 137 

 151 

 150 

 188 

 185 

 154 

 132 

 135 

 148 

 156 

 156 

 159 

 112 

 134 

 116 

 126 

 164 

 175 

 120 

 127 

 173 



168 

 137 

 129 

 133 

 150 

 124 

 146 

 150 

 173 

 144 

 169 

 168 

 133 

 131 

 135 

 120 

 117 

 112 

 108 

 123 

 106 

 107 

 109 

 099 

 121 

 113 

 107 

 114 

 122 

 126 



110 

 111 

 093 

 126 

 094 

 101 

 102 

 106 

 143 

 105 

 094 

 095 

 104 

 112 

 100 

 117 

 107 

 122 

 121 

 110 

 125 

 148 

 111 

 084 

 i)93 

 099 

 092 

 068 

 096 

 089 

 110 



118 

 102 

 118 

 122 

 138 

 134 

 105 

 127 

 152 

 131 

 103 

 081 

 087 

 075 

 084 

 115 

 115 

 114 

 112 

 131 

 131 

 127 

 130 

 100 

 135 

 114 

 135 

 125 

 131 

 135 

 126 



155 

 140 

 124 

 139 

 112 

 106 

 134 

 173 

 131 

 126 

 127 

 159 

 170 

 162 

 118 

 156 

 137 

 152 

 170 

 113 

 133 

 139 

 173 

 169 

 130 

 115 

 154 

 123 

 165 

 190 



163 

 198 

 211 

 161 

 166 

 171 

 186 

 163 

 167 

 126 

 173 

 175 

 181 

 203 

 211 

 140 

 162 

 172 

 196 

 172 

 161 

 239 

 225 

 249 

 207 

 227 

 247 

 212 

 246 

 179 



178 

 186 

 189 

 219 

 196 

 239 

 281 

 237 

 155 

 184 

 180 

 206 

 215 

 179 

 236 

 303 

 281 

 235 

 218 

 224 

 205 

 235 

 243 

 203 

 237 

 226 

 171 

 171 

 229 

 283 



235 

 216 

 232 

 266 

 199 

 231 

 256 

 216 

 271 

 239 

 145 

 224 

 250 

 218 

 215 

 190 

 242 

 257 

 244 

 237 

 270 

 251 

 238 

 233 

 195 

 170 

 213 

 225 

 215 

 222 

 225 



6.978 

 .2251 



16. 387 

 6. 579 



2278 



6.476 

 .2089 



5.558 

 . 18.53 



4.672 3.894 

 1507 .1298 



3.288 

 1061 



3.713 

 1198 



4.295 

 1432 



5.914 6.544 

 1908 .2181 



7.040 

 . 2271 



An inspection of this table shows a marked annual variation. To 

 exhibit its law, the monthly means at the foot of the table were first 

 corrected for the unequal length of the months, and then used to com- 

 pute coefficients for Bessel's periodic function. The resulting formula 

 is the following : 



D=0.17754-.0607 sin (^-f76o.l) + .0094 sin (2^+218o.O) 

 + .0036 sin (3^+275o.6) + .0016 sin (4^+259o.6.) 



The coefficients of the five terms here given exhibit a more satisfac- 

 tory convergence than any five successive terms in the formula for the 

 annual fluctuation of pressure, and indicate that the function in ques- 

 tion — the amount of atmospheric disturbance — is entitled to considera- 

 tion as a meteorological element governed by a simple law of change. 

 By differentiating the formula the function is found to have two nearly 

 equal maxima on December 11 and February 4, of which the latter is 

 the higher, their respective values being 0.2261 and 0.2275. Between 



