Date.
117
8. As stated in the "Instructions for making Meteorological Observations," meteorological in- struments forwarded by observers who regularly send their registers to the Observatory are verified here free of cost. During the past year, I thermometer was verified and several hundred barometers and aneroids on board ship were compared with our standard.
9. The mean values of the spectroscopic rainband (1-5) in 1901 were as follows:- -January 2.0, February 1.0, March 1.8, April 2.2, May 2.6, June 2.1, July 2.1, August 2.2, September 1.8, October 1.7, November 1.0, December 1.3. Year 1.82.
10. In 1901, the number of transits observed was 3,349. The axis of the transit instrument was levelled 231 times and the azimuth and collimation errors, which are less liable to variation, were determined 28 times by aid of the meridian mark erected in 1884. Stellar observations were discon- tinued between June 3 and August 2, and again between September 19 and November 20. About one half of the observations have been made and the whole have been reduced by Mr. J. I. PLUMMER, the remainder of the observations have been made by Mr. F. G. FIGG and myself.
11. The standard sidereal clock by Dent has gone uninterruptedly thoughout the year in a per- fectly satisfactory manner. The platinum points of the contact springs were cleaned once only, viz., on August 29, an operation which does not appreciably interfere with the rate, but usually alters the arc of vibration to some extent. The standard mean time clock by Brock continued to go in the unsatisfactory manner mentioned in previous reports until June 4, when, the cord of the driving weight, having been found broken, the clock was thoroughly overhauled, and the pendulum taken to. pieces and cleaned. As the compensation of this clock was much in excess, the zinc tubing was short- ened three millimetres, and there is reason to believe that the going of the clock since these alterations. has been materially improved. The time-ball clock continues to give satisfaction.
The
12. The errors of the time-ball are given in Table II. There were six failures in 1901. ball is not dropped on Government holidays, nor, since December 1st, on Sundays, and on 50 days this year it has been under repair. The cause of the failures on February 17, June 6 and June 10, was that the piston jammed at the top of the shaft most probably in consequence of hardened oil in the shaft on the first occasion, and from rust on the mast upon the later dates. On July 20 the current failed to discharge the lock, and on November 21 and November 25, the back spring having become loose, the piston would not rest upon the tooth. The ball was dropped successfully 286 times in the year, and on five days was not dropped, there being no assistant available. In consequence of the repeated repairs necessary to the old ball, the zinc having become crystallized and very much cracked, a new one was ordered from the Hongkong and Whampoa Dock Company which has been erected and which was dropped for the first time on August 23. The new ball has been constructed of brass with spring steel ribs, and to obviate any accumulation of rain-water in the interior of the ball, a small hole has been drilled at the lowest part of its circumference. The probable error was in January 0.22. in February± 0.09, in March + 0.12, in April ± 0.28, in May ± 0.11, in June ± 0.11, in July± 0.10, in August ± 0.09, in September ±0.10, in October± 0.09, in November ± 0.10, and in December ± 0.20.
Table II.
Ervors of Time-Ball in 1901.
means too late.
+ means too early.
Jan.
Feb. March.
April. May.
June.
July.
Aug. Sept.
Oct.
Nov.
Dec,
05-1
01
01
01
01
01
051
0-1
+02
+0.3
0.1
+0.2
0.1
+0.2
0.1
0.1
+0-6
3
+054
0.1 +0.2
+0.4
0.1
0.1
0.1
0.1
0.1
+0.6
+0.2
0.1
0.1
+0.3
0.1
+0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
+0.3
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1 +0.3
0.1
0.1
0.1
0.1
0.1
0.1
7
+0.2
0.1
0.1
0.1
0,1
-0.2
0.1
0.1
0.1
0.1
+0.4
0.1
0.1
+0.2
0.1
-0.2
0.1
0.1
0.1-
9
+0.6
0.1
0.1 +0.7
+0.2
0.1
0.1
0.1
0.1
0.1
10 +0.7
0.1
0.1
+0.9
0.1
0.1
0.1
0.1
11 +0.9
0.1
0.1
+1.1
0.1
0.1
0.1
+0.2
12 +0.6
0.1
0.1
+1.3
0.1
+0.3
0.1
13
+0.5
0.1
0.1
+1.4
0.1
-0.2
+0.2
01
-0.2
14
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0:1
15
-0.2
0.1
0.1
0.1
0.1
0.1
0.1
16
0.1
0.1
0.1
0.1
0.1
0.1
0.1
17
0.1
+0.2
0.1
0.1
0.1
0.1
0.1
18
0.1
0.1
0.1 +0.2
0.1
0.1
0.1
0.1
3333333
0.1
0.1
+0.2
0.1 0.1
0.1
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