TABLE II. Reading of the Barometer (reduced to 32° F.) minus mean of day. The Barometer was not read at the exact hour, but at 23 mins. before; thus midnight is really 11h 573 p.m. (Unit = 0.0001 inches.) Hour. Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Midn. +45 +100 +119 +112 + 88 +81 +112 +131 +163 +96+62 + 72 324 337 340 340 298 248 243 280 306 286 20 +60 +9+40 +48 + 76 +85 + 96 +105 +138 +129 + 90 + 56 21 168 128 180 158 169 164 174 191 251 231 204 171 264 199 194 197 204 231 287 293 277 259 Month. DIURNAL VARIATION OF TABLE III. THE BAROMETER AT ST. HELEN A. C1 S1 C2 S2 C3 S3 C4 S4 C5 S5 C6 S6 C1 S7 C8 S8 C9 S9 C10 S10 C11 S11 C12 Aug. 10.0 32.0 287 2 July +102-18'0 +116'4-2226- 62-44'8 +06-15'0 – 0·5 · 130 8 245'9 7.2 30.90'8 13.2 4.0 3.0 17 4.2 1.8 133'8 272.2 119.8 24-09+10'4+13 +13-05 +04 +03-15 +05+01-27-02-16 5.9 06 17 1.3 2.1 01-04 1'3+14+0°2 10:4 11.7+37 9.5+22+ 02+02 0.9 6.4 3.3 08-19-30+01 0.7 04 04-03-09 16.9+10:0 4.3 5'7 2.2 6'4 14 118.3 286 2 10.4 34.2 1.7 4.2 4.7 6'4 0'4 3.8 8.3 6.8 6.7 13'4 43.8 6.9 2.9 2.6 10.6 6.2 4.9 252.1 12.7 20.8 2.6 8:0 0.2 Mar. 41.8 76.5 161 2 271.3 10.9 01-11 9.7 3.9 April 50.0 93.0 144 8 13.4 May 39.8 64.8 272.0 21.1 4.1 8.9 1'1 12.7-1.2 13-115+32-21+0'5 2.3 2.1+0.5 0'1+2 3+17 +0'6 0'2-13-09-08 3.0 1.5 8551-28-15 19 2.51'60'4] 0.4 0'6 0'4 0.3 0.2+1.8 1.5 13+01+20 0'8 TABLE V. Seasonal Variation of the Coefficients of the Diurnal Variation of the Barometer as functions of the Sun's mean Longitude. (Unit = 0.0001 inch). (c) DURBAN, NATAL OBSERVATORY, 1873-1905. The monthly means given in the table are derived from two sets of observations. From 1873-1883 the readings were taken in the Botanical Gardens, Durban, which are close to the Observatory, (Govt. Astronomer's Report for 1903). Observations were made at 9 a.m. and 3 p.m. It has been assumed from the observations themselves, that in the mean the difference of the reading 9 a.m.-3 p.m. is as follows: The mean of the 3 p.m. readings thus increased, and the 9 a.m. readings has been taken as the 9 a.m. reading. When this mean deviates more than 0.015in. from the 9 a.m. reading : is added as added to the figures printed in Table 1. It has been further assumed that in the mean of 11 years, these readings reduced to sea-level should agree with the mean of all the reduced readings taken at the Durban Observatory. To force this agreement -0.038in. has been applied to all the readings taken at the Botanical Gardens. The observations since 1884 have been made at the Natal Observatory. In deriving the 9 a.m. means, we have in general three sets of figures, viz., the 8 a.m. readings published by the Cape Meteorological Commission, and the 9 a.m. and 3 p.m. readings published by the Government Astronomer. It has been assumed that in the mean the difference between the 9 a.m. reading and the 8 a.m. and 3 p.m. readings are as follows: The mean 9 a.m. reading is the mean of the three reduced readings, but discordant readings have been rejected. The heights of the Durban barometers have been The reduction from mean of year at 9 a.m. to mean of day is about -0.033 inches. I have to thank Mr. Nevill and Mr. Fermor Rendell for their assistance in clearing up some doubtful printings and readings. |