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426
THE HONGKONG GOVERNMENT GAZETTE, 15TH MAY, 1886.
The moment the clock closes the local circuit at 1 o'clock, the change of direction of the current and its almost instantaneous cessation consequent on the break of the circuit by the act of discharge, is seen on the galvanometers. Should there be any delay in the fall, both observers see this on the respective galvanometers, the needles being then permanently deflected. But so rapid in practise is the discharge and the consequent break of the circuit, that the needles are scarcely deflected at all towards the sides of the galvanometers, where the word "discharged" is engraven, and if the time elapsed between the second hand of the clock stopping at 0. and the hand of the galvanometer, giving the return signal from the tower, amounted to nearly of a second, the delay would be noticed in the observatory. The discharge of the current at 1 p. is observed on the sidereal standard clock, furnishing a final ocular demonstration of the ball dropping correctly.
Ι
The accuracy of the 1 o'clock signal depends therefore practically only upon the error of the standard clock being accuratety determined. This can always be done within of a second when the weather permits transit observations to be made the previous night. Whenever no observations are available, we depend entirely upon this clock keeping a regular rate. reason impossible to drop the ball without error, the latter becomes known from subsequent observa- But although it is for this tions. The following table exhibits the errors of one o'clock signals in 1885, for every day on which the ball was dropped. Whenever the error was less than 0.15, 0.1 has been entered without sign:
ERRORS OF TIME BALL IN 1885.
means too late, + means too early.
Date.
Jan.
Feb.
March.
April.
May. June. July. Aug.
Sept.
Oct.
Nov. Dec.
0.'1
་་-
0,"1
0."1
0.*1
0.51 -0."4
0.1
0."1
+0.82
+0.6
0."1
+0.2
0.1
0.1
0.1
-0.2
0. 1
.0.2
+0.7
0.1
0.1
0.1
+0.2
...
0.1
-0.2
0.1
0.1
0.1
-0.2
0.1
0.1
0.1
0.1
0.
0.1
-0.7
0.1
0.1
0.2
-0.4
0.1
+0.3
-0.2
0.1
-0.6
+0.3
0.1
0.1
0.1
+0.2
0.1' +0.5
-0.3
0.1
+0.3
0.1
0.1
0.1
0.1
0.1
0.1
+0.2
-0.4
+0.3
0.1
0.1
0.1
0.1
0.1
+0.8
0.1
-0.5
0.1
0.1
0.1
9
0.1
+0.4
-0.2
:
0.1
+0.5
+0.2
0.1
0.1
+0.2
0.1
10
0.1
0.1
+0.3
0.1
-0.2
+0.3
0.1
+0.2
0. 1
0.1
11
+0.2
+0.5
0.1
-0.3
+0.2
0. 1
0.1
0.1
-0.3
12
0.2
+0.4 -0.3
+0.2
0. I
-0.2
0.1
...
0.1
13
0. 1
0.1
0.1
+0.8
0. 1
-0.4
+0.4
-0.3
0.1
-0.2
14
0.1
-0.2
0.1
0.1
-0.4
0.1
*
-0.3
...
0.1
0.1
15
0.1
0.5
-0.2
-0.3
0.1
0.1
+0.5
-0.2
-0.8
0.1
16
-0.-3
-0.3
0. 1
0. 1.
0.1
0.1
0.1
17
0.1
0.
-0.3
-0.5
0. I
0.1
0.1
-0.2
-0.2
-0.3
0.1
18
0.
-0.7
0. 1
0.1
-1.0 -0.3
-0.2
-0.3
-0.3
19
0.
-0.5
-0.2
-0.9
+0.2
-0.5
+0.2
-0.3
0.1
20
-0.2
0.1
0.2
0. 1
0.1
0.1.
-0.7 -0.2
--0.3
0.1
21
-0.2
0.1
0.9
0.1
0.1
-0.9
-0.9
+0.2
0.1
0.1
-0, 3
22
0.1
+0:2
•
0.1
-1.1
0.1
0.1
0.1
0.1
-0.2
23
0.1
+0.2
0.1
+0.2
0.1
-1.3
0. 1
+0.2
0,1
-0.3
0.1
24
-0.2.
+0.2
0.1
0.1
0. I
0.1
+0.2
+1.0
0.1
-0.4
0.1
25
-0.3
+0.2
0-1
-0.2
+0.4
-0.2
0.1
0.1
26
-0.3 -0.3 +0.2
0.1
0.1
27
-0.4 -0.2 +0.3 -0.2
- 1.0
0.1
0.1
0.1
0.1
-0.5
0. 1
-0.2
0.1
28 -0.5 -0.4 +0.5
0.1
+0.2
0.1
+0.3
-0.3
-0.2
0.1
29
-0.6
0.1
+0.3
0.
-0.7
+0.4 -0.5
0. 1
30
-0.3
31
0.1
+0.2 0.1
.0.1
0.1
0. 1
-0.2
0.
+0.5
0.1
0.1
0.1 0. 1
0.1
-0.3
-0.4
The probable errors of the signal in the different months of 1885 (with the average amount of clouds added in parenthesis) were as follows:
January 0.18 (69), February 0.27 (94), March 03.16 (70), April 0.'15 (76), May 0o.29 (74), June 0.13 (74), July 0.20 (74), August 0.24 (75), Setember 0.15 (65), October 0.16 (50), Novem. ber 0.14 (46), December 0.19 (43).
As stated in the time-ball notice, the ball is not dropped on Sundays or on Government Holidays. On the 6th of January it failed at 1 p. (the single cell of the clock circuit failing to act) but was dropped at 2 p. On the 20th and 21st April thunderstorms prevented the working of the apparatus. On the 13th June the wires of the coil of the lock were found to have been fused by the lightning on the previous evening but the ball was dropped at 2 p. On the 27th August notice was given that the ball would not be dropped for a few days owing to damage done by the thunderstorm on the 25th, and it was not dropped on the 27th, 28th and 29th. From the 7th to the 20th September inclusive the apparatus was not worked owing to fever among the staff of the observatory. It is seen, that the signal never failed to act on any day in 1885. It failed partly (ball dropped at 2 p.) on 2 days. Thunderstorms prevented the signal on 5 days and illness among the staff on 12 days.
As stated in the Annual Report, the lock sent out with the time-ball was not fit to drop the ball, the blow of the hammer failing to liberate the bolt unless the spring was tightened so excessively as to make the equilibrium of the hammer unstable. Under these circumstances the dropping of the ball
X