METEOROLOGICAL REGISTER KEPT AT
THE
188
Wind. Clouds. Ther- Hour. Att. Baro- Ther. Max-| Min- meter. mom-eter. imum., imum. Direc- Am- Whence coming. Wea- Sea. REMARKS. ther. Force. tion. ount. Lower. Upper. O ins. O 0-12 | 0-10 * 0-9 1 A.M. 4 A.M. 7 A.M. 10 A.M. 1 P.M. 4 P.M. 7 P.M. 10 P.M. Sum. Mean.INSTRUCTIONS
FOR MAKING
METEOROLOGICAL OBSERVATIONS
PREPARED FOR USE IN CHINA BY
W. DOBERCK,
Government Astronomer.
Observer.
PREFACE.
These instructions are issued for the information of meteorological observers in the treaty ports of China, which extend as far north as Newchwang (latitude about 41° north, longitude about 122° east of Greenwich) and as far west as Hankow and Ichang, both on the Yangtze-kiang, far inland in China, for the information of observers in the Colony of Hongkong, and for the use of commanders of vessels of all nationalities, who frequent the China seas, and to whom a knowledge of atmospheric circumstances will be especially useful, not to say necessary for the safe navigation of their ships.
Meteorological registers or logs kept according to these instructions will be thankfully received at the Hongkong Observatory, where intending observers are invited to apply for any further information which they may require, with regard to the purchase of meteorological instruments, or with regard to the observations.
It is to be hoped that the instructions will be followed by all the observers in these regions, as meteorological observations which are not made according to a plan generally adopted are seldom of any use.
II-Barometer.
1. With the barometer we measure the pressure of the atmosphere. It consists of a vessel containing mercury (the cistern), in which is inverted a glass tube filled with pure and dry mercury. It has been boiled in the tube in order to expel every trace of air or dampness.* In virtue of the law of hydrostatic pressure, when the tube is inverted and
*Pure mercury has a bright surface and there are no air-specks visible even with a magnifying glass. But to test the vacuum the barometer must be slowly inclined till the mercury reaches the top of the tube. If a metallic click is not heard at the moment of contact, there is air above the column. To invert the barometer and leave it for some time inverted will usually cause the air, if present in only a small quantity, to rise and leave the column.
Page 15
Page 16