The Barometer in South Africa. 95 



3— BAROMETER OBSERVATIONS, 

 (a) Royal Observatory, Cape of Good Hope, 1841-1905. 



Readings of the Barometer at the Cape Observatory are available 

 (with the exception of a few slight interruptions in the earlier years) 

 since April, 1841. 



From 1841 to 1846, the observations were made under the general 

 direction of Sabine, and since that date, under the direction of H.M. 

 Astronomers at the Cape. The observations made from 1841 to 1846 

 have been published at length (Observations made at the Mag. and 

 Met. Observatory at the Cape of Good Hope. Vol. 11., Metsrological 

 Observations. London, undated). These, with the observations to 

 1870, were discussed and published by the late E. J. Stone (Results 

 of Met. Observations, Cape Town, 187 1). Since 1875, the monthly 

 means have been published in the annual reports of the Cape 

 Meteorological Commission. 



There were several reasons which made it desirable to re-discuss 

 the whole series from 1841 to date. The volumes containing the 

 results to 1870 are not common; the observations 1871-74 have never 

 been printed ; and several of the Cape Meteorological Commission 

 Reports are unobtainable. Then it is necessary to reduce the whole 

 series in a homogeneous manner. This involves the reduction to the 

 mean of the day, as it is obvious, for example, that the means of 

 observations taken at 9 a.m. will be quite different from those taken 

 to I p.m. and so on. 



From 1 841 to 1846, hourly or two hourly observations were taken. 

 From 1846 to 1870, five observations a day were taken — the reduction 

 to mean of day for this series, only amounts to o.oo2in. during the 

 month of October, — this reduction has only been applied between 

 1847 and 1850. From 187 1 onwards, the hours of observation have 

 varied as follows : — 



1871-72 At 3, 9, 15 and 21 hours, mean local time. 



1873 At 9, 15 and 21 hours. 



1874-1878 Jan. II At o, 6, 12, and 18 hours. 



1878 Jan. i2-Dec. 31 At o, 6, 13I, and 18 hours. 



1879-1880 At 6, 13I,, and 18 hours. 



1881-1883 At 6, 13I, and 22 hours. 



1884-1889 At 8 and 13^ hours. 



1890 At 8, ij, and 20 hours. 



1891-1892 Feb. 7 At 8, 12, and 20 hours. 



1892 Feb. 8, 1902 At 8*, 12, and 20* hours. 



To reduce to mean of day, we have at our service, Stone's Table 

 XIII. in the volume already quoted. This table has, however, not 

 been used. Inspection of it indicates the presence of anomalies in 

 the observation of 1841-1846 on which it is based. The exposure of 



* Mean Time of 22^° E. 



