WHOLE VOL. NOTES. AFRICA 23 



The heii,'lits given are derived from the Ivailway Levels. No 

 ]>recisc levelling has been carried out in the Colony 

 yet, but the altitudes of certain stations in the pri- 

 mary triangulation of the country were fixed by 

 the Geodetic Survey by means of angular measure- 

 ments and corrected to height above Mean Sea 

 Level bench marks at Delagoa Bay, Port Natal, 

 Algoa Bay and Cape Town, with a probable error 

 of ± 15 ft. According to the Geodetic Survey level, 

 the altitude of Salisbury station as derived from 

 the railway levels is 45 ft. too high. The heights 

 as given are therefore only approximate and may 

 be from 30 to 60 ft. too great. 

 liish'uiiiciits: 



1897 May to 1900 November 19. Kew Pattern, no. 2006. 



1900 November 20. Kew Pattern, no. 2397. 



1917 to 1921 Augu.st. Fortin Barometer M. O. no. 1331, 

 with index error correction of +0.003 "i- 



The exact date of the installation f)f the Fortin barometer 

 ?\L ( ). no. 1331 is not known, but it was after 1910 

 and ])rior to 1917 and it appears probalile that it 

 may have been installed after the break in the 

 recorfls in 191 1. 



192 1 September to 1923. Barometer and correction 

 unknown. 



The index error corrections to the two first instruments are 

 not known, as the date at which barometer M. O. 

 T331 was brought into use is not known exactly, 

 the index correction of +0.003 ""i- ^""^s been ap- 

 plied to the whole series up to 1921 (August). 

 Hours: The observations were taken at 9'^ (30tli meridian 



time) throughout the period. 

 A'otcs: All values have been corrected to normal gravity (Lat. 

 45°) by applying a correction of —0.055 i"- 



There may be some doubt as to the absolute accuracy of the 

 pressure record during the period in which it was 

 taken at the Gaol. 

 Temperature. 

 Site : 



1897 '^^''.y to 1921 y\ugust. As for Pressure. 



1 92 1 September to 1923. Observations were continued at the 

 Gaol. 



