566 MR J. A. BROUN ON THE 
TABLE I.— Range of the Mean Diurnal Variation of Magnetic Declination for each Month, 
1853 to 1876, at Trevandrum. 









| Year. Jan. Feb. Mar. | April. | May. | June. | July. Aug. | Sept. Oct. Nov. 
1853 | [2°40]| 2°37 | 1°08 | 1:35 | 2°90 | 355 | 3°51] 4:10] 4:29] 1°07 | 2°15 
1854 | 2:18] 1-65 | 0-57 | 1-81 | 3:20} 3-04 | 2-90] 3-30] 3:21 | 1:29] 2-26 
1855 | 2-10 | 1:65 | 0-67} 2-05 | 2-76 | 2°88 | 2-71 | 3-19] 3-23] 1:14] 1:52 
1856 | 1-93 | 1-40 | 0-85 | 1327 1-97] 2:47 | 2-71] 320] 2-72] 1-07] 2-18 
1857 | 1:82 | 1:69 | 0-95] 1:34 |. 3:05 | 2:32 | 2:54] 318] 3-79 | 0-99] 1-78 
1858 | 2-41 | 1:59 | 1:26] 1:95 | 2:86 | 2-92] 3-36] 3-78] 2:83 | 1.09 | 2.71 
1859 | 2:24 | 1:69 | 1:02] 1:96] 329] 3-44] 3-44] 362] 3-71] 1-62] 2:59 
1860 | 2:73 | 2:03 | 169] 2:27] 354] 3.64] 3:35 | 5-32] 359] 1-73 | 2-46 
1861 | 1:79 | 1:08 | 0-78 | 1:33] 277] 332 | 3-43] 4:51] 3-72] 148] 2-03 
1862 | 2:32 | 1:28 | 0-85] 1:60 | 2:79 | 3:36 | 2-72] 2-84] 2:98] 1:25 | 2:36 
1863 | 2-48 | 1-49 | 0-85] 1:56 | 3:00 | 2:86] 3-34] 318] 264 | 1:36 | 2-19 
1864 | 1:99 | 1:65 | 0-35 | 1:54] 3:09 | 3:22] 2-86] 3-73] 3-40] 1-44] 1:68 
1865 | 2-45 | 1-94] 0-75 | 1:96 | 2:81 | 2:91] 2-49] 3-18] 2-67 | 1:45 | 2-01 
1866 | 1:51-| 1:95 | 0-62] 1:38 | 2:27 | 2°59 | 2-09 | 230] 2:59 | 1:36 | 2-07 
1867 | 1-44 | 1:51] 0-73 | 1:95 | 2°36 | 2:46 | 2-62] 2-75 | 1:81] 151 | 2-18 
1868 | 164] 1:60] 0-97 | 2-16 | 2°67 | 2:94] 2.32 | 358] 2-94 | 1:13 | 2-05 
1869 | 326 | 2:19 | 0-69 | 1:79 | 3:29 | 3:81 | 3-82] 3-89] 2-84 | 1:58] 2:47 
1870 | 2-15 | 1:34] 0-91] 1:82 | 3:08] 4:27] 4:33] 4:96] 4-09 | 114] 2-03 
1871 | 281 | 2-24] 0-74 | 2:60] 3:01 | 3:92 | 4:01 | 4-65 | 3°39 | 1:59 | 2-43 
1872 | 2-42 | 2:23 | 0-61 | 2:08 | 3:49 | 3:37 | 3-62] 3:97] 4:00 | 1:19 | 2-47 
1873 | 2:26 | 1:96] 0-63] 1:39 | 3:27] 2-91] 350] 3-75 | 3:15 | 116] 1-68 
1874 | 1:97 | 2-24 | 1-00] 1-79 | 2°57 | 260] 2:20] 2:91 | 3-02] 1:20] 1-54 
1875 | 1-70 | 1:80 | 0-76 | 0-96 | 3:02 | 2:54 | 210] 2-88] 2:93 | 1:35] 1-48 
1876 | 1-56 | 1-82 | 0-68 | 1:20 | 266 | O96 1 1s ee eee 


8. In order to obtain the epochs of maximum and minimum oscillation it 
has been usual to employ only the yearly means corresponding (for their middle 
points) to the 1st July. Ihave sought more complete results by taking the 
yearly means corresponding to the Ist of each month;* these are given in 
Table II., where the quantity under each month is the mean range deduced 
from the oscillations for six months before and six months after the first of that 
month. These quantities are projected in Plate XX XIX. 
9. From Table II. we obtain at once the following epochs with the corre- 
sponding values of the yearly mean range. 
Minimum, 1856°3. Range, 1°88. Maximum, 1860°3. Range, 2”98. 
1866'5. sy, le DOE $5 LSi0p86: eee 
9 
From the nearly constant and low value (2’01 to 197) for the 12 months, 
corresponding to Ist November 1874 to 1st April 1875, I have concluded that 
the minimum is again nearly attained.t 
* This method was employed by me previously for the daily and monthly means of horizontal 
magnetic force.—Trans. Roy. Soc, Edin., vol. xxii. plates xxv., xxvi, and xxviii. 
+ I have been able, before printing, to add the means for several months later than those in my 
possession when this paper was written. 

