264
TABLE III.
Errors of Time-Ball in 1889.
means too late.
+ means too early.
Date.
Jan.
Feb.
March. April, May. June. July.
Aug.
Sept.
Oct. Nov. Dec.
1,
0.1
+0.2 +0.8 +0.5
0.1
0°.1
0.1
0.1
0'.1
2,
0.1
0.1
+0.2
+0.8 +0.6
0.1
0. 1
0°.1
0.1
0.1
.0'.5
3j.
0.1
+0.9
+0.2
0.1
+0.2
0.1
-0.2
-0.2
0.1
0. 1
+0.3
+0.9 +0.7
0.1
+0.2
0.1
0.1
0.1
-0.5
5,
0.1
0.1
+0.4
+0.7
0.1
0.1
0.1
0.1
0.1
+0.2
6,
+0.2
0.1
0.1
0.1
0.1
0.1
+0.5
0.1
-0.2
0.1
7,
-0.5
0.1
0.1
-0.2
0.1
0.1
0.1
...
0.1
-0.2
0.1
8,
-0.7
-0.2
+0.2 0.1
0.1-
0: 1
0.1
0.1
0.1
-0.3
9,
0.1 -0.4
+0.2 +0.2
0.1
0.1
0.1
0. I
0. I
0.1
0. 1
10,
0.1
+0.3
0.1
0.1
0.1
0.1
0.1
-0.2
11,
+0.2
-0.2
+0.4 +0.4 +0.2
0.1
0,1
-0.3
0.1
0. 1
12,
+0.3
0.1
+0.5
0.1
0.1
0.1
0.1
0. 1
0.1
0. 1
0.1
13,
0: 1
+0.6
+0.2
+0.4
+0.2
0. I
0. 1
-0. 1-
-0. 3
14,
+0.7
+0.2
+0.2
+0.5
0.1
0. 1
0. 1
0.1
-0.2
0.5
15,
0.1
0.1 +0.2
+0.5
+0.6
0.1
0.1
0. I
+0.2
0.1
-16,
0.1
0.1 +0.3
+0.6
0.1
·0. 1
·0. 1
0.1
0.1
.0.1
17.
-0.2
0.1
0.1
0.1
+0.3
0.1
+0.3
0. 1
18,
-0.3
+0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
+0.2
+0.2
19,
-0.5
0.1
-0.2
0.
0. 1
0. 1
+0.2
0. 1
+0.4
0. I
20,
+0.2
0.1
+0.2
-0.3
0. I
+0.2
0.1
0.1
+0.6
21,
0.9
0. 1
0.1
0. I
0. I
+0.3
0.1
0.1
0.1
22,
- 1.1
0..1
0.1
0.1
0. I
+0.3
+0.4
+0.3
23,
0.1
0. 1
+0.2
0.1
0.1
0.1
+0.2
+0.4
0.1
24,
-0,2
-0.2
0.1
+0.2
0.1
+0.3
25,
0.1 +0.2
+0.3
0.1
0. I
0.
26,
0.1
+0.2
+0.3
0.1
-0.2
++
+0.4
+0.6
0.1
+0.6
+0.5
27,
+0.2 +0.4
0. I
0. I
0. 1
0.1
-0.2
0.1
0.1
0.1
28,
0.1
+0.4
0.1
0. I
0.1
0. 1
-0.2
-0.3
29,
0.1
+0.5
0. I
0.1
-0.2
0. 1
-0.3
30,
+0.2
+0.7
+0.3
0. 1
0.1
0.
-0.4
0.1
31,
:
-0.3
-0.2
0. 1
0, 1
0.1
17. The probable errors of the signal in the different months of 1889 (with the average percentage of clouded sky added in parenthesis) were as follows:-
January 0.24 (86), February 0.13 (62), March 03.23 (94), April 0.28 (84), May 0.20 (81), June 0.09 (76), July 0.12 (50), August 0.12 (63), September 0.13 (57), October 08.10 (57), November 0.20 (62), December 0.16 (60).—The mean of the probable errors was'0)3.17.
=
=
=
=
18. During the past five years the time-ball has been dropped 1465 times, or perhaps about 1500 times if the experiments be taken into account.-An error of less than 0.15 occurred 804 times, of 0°.2 249 times, of 0.3 142 times, of 0.4 88 times, of 0.5 61 times, of 0.6 = 36 times, of 0.7 30 times, of 0.8 16 times, of 0.9 15 times, of 1.0 9 times, of 1.15 times, of 1.2 = 3 times, of 1.3 = 3 times, of 1.4 = 1 time, of 1.5= 2 times, of 1.6 = 1 time.-From this distri- bution of errors it appears that the accuracy of the signal has been under-estimated. In the calculation in fact all errors less than 0.15 have been taken as equal to 01:-With the value of the probable error 0.15, which follows from the figures, we obtain for the frequency of errors less than 0.15 = 733, of 01.2 — 350, of 0o.3 = 213, of 0.4 106, of 0.5 43, of 0.6 15, of 0.7 4, of 0.8 = 1. The occurence of errors more than five times as large as the probable error is common enough in practise although it is not explained by the theory of least squares in the form in which it is given in the text books.
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19. As stated in the "Instructions for making Meteorological Observations, etc." meteorological instruments forwarded by observers who regularly send their registers this Observatory, are verified here free of cost. During the past year, the following number of instruments was verified and certi- ficates issued:-Barometers 3, Thermometers = 6. The index errors of barometers read off on board ship are determined whenever required by comparing readings made near this port with the barograms.
20. In the "China Coast Meteorological Register," based on information transmitted by the Eastern Extension, the Great Northern and the Imperial Chinese Telegraph Companies, which was daily published is given a summary of the atmospheric circumstances in the Far East. It contains also in- formation concerning the first appearance and progress of typhoons and gives an account of all storm- warnings issued.
21. From 3.30 p. on the 29th of May till the same time on the 30th there fell 22.535 inches of rain. This occurred during thunderstorms of unusually great duration. The floods caused by the rain proved a disaster to the Colony. Roads and streets were cut up, retaining walls carried away, sewers burst and houses undermined, but only few persons were killed by the lightning.
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