VV

Code X. — Barometric Tendency.

By the " barometric tendency at a given hour " is meant the amount by wliich the barometric height has changed during the preceding three hours. It is to be expressed in millimetres. For example, the barometric tendency at 8 a.m. could be obtained by comparing the reading taken at that hour, say 75.5' 7 mm., with a reading taken at .i a.m., say 759'o mm. In this case the barometric tendency would be expressed by a fall of 3*6 millimetres. As a general rule the barometric tendency is to be determined from the trace of the barograph.

The barometi'ic tendency is coded in two figures, according to the following table : —

Rise in Barometer.

Fall in Barometer.

Code No.

Code No.

Millimetres.

Inches.

Millimetres.

Inches.