20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 79 



1901 June to 1920 December. Nigeria Government Gazettes 

 with the exception of : 

 1914, November and December; 1915, September to 

 December; 1916, 1917, 1918, 1919 and 1920, Janu- 

 ary, for which months the data were extracted from 

 the Nigeria Blue Books. 

 C Jiang es of Site : 



1 89 1 to 1896 November. 25 ft. 

 1896 December to 1920. 22 ft. 

 C Jiang es of Instrument: 



In 1 89 1 January, a Marine Barometer, no. 657, index error 



correction —.005 in., was in use. 

 In 1922 January, a Fortin Barometer, no. 2304, Negretti and 

 Zambra, index error correction +.003 in. was in 

 use. The date of change is unknown. 

 Clianges of Hours of Observation: 

 1891 to 1901 February. 8'\ i6'\ 



1901 March to 1901 September. 9'^ 16^. 

 1903 October to 1920. g^, 15''. 



These hours have been taken as comparable. The hours from 

 1 901 October to 1903 September are unknown, but 

 are probably 9'^ and i6'\ 



For the months taken from the Nigeria Blue Books (see 

 Authorities) the observations are at 9'' corrected 

 to i(9'^+I5'^) by the following corrections: 



Jan. Feb. Afar. Apr. Jfay June July Aug. Sept. Get. Nov. Dec. 

 Indies —.052 — .O.'.O —.040 —.043 — .OJl —.039 —.041 —.046 —.048 —.047 —.047 —.050 



Notes: 



A correction, —.076 in., to reduce values to normal gravity 



at Lat. 45°, has been applied throughout. 



1891 to 1896 November. A correction of +.003 in. has been 



applied to reduce values to height of 22 ft. 



1902 July to 1905 April. For some unknown reason the 



pressure readings for this period were obviously 

 too high. A correction of —.040 in. has been de- 

 duced by comparison with the readings at Sierra 

 Leone and has been applied. 

 191 1 January to 1915 May. The data for this period had 

 been corrected to Mean Sea Level and have been 

 brought back to a height of 22 ft. by a correction 

 of —.023 in. 



