154 APPENDIX B
METHOD OF REDUCTION, 1913-15 JOURNEY
Hypsometer readings, corrected for thermometer scale-error, were reduced to equivalent air pressure, and these were treated as fully corrected. Mercury barometer readings were corrected for scale-error and reduced to freezing point. Aneroid readings were treated as fully corrected. In this way each instrument yields a fully corrected pressure.
Next from a table, based on the International Meteorological Formula (1905) the height above a standard pressure level, 29.92, was read off. The result was multiplied by a factor, taking account of the mean air temperature. By means of the Indian Daily Weather Report chart, the value of pressure at sea-level at the station is estimated. Its difference from the value 29.92 multiplied by 873 is the necessary correction to the height in feet.. The differences between results of aneroid and mercury barometer were taken out, and applied to succeeding aneroid readings until the next comparison occurred. The same would have been doue for the hypsometer results, if it had been decided to retain them.
MISTAKES OF COMPUTATION
By a mistake on the part of the computer, uncorrected aneroid heights were given in
RECORDS AND COMPUTATIONS
These are at Dehra Dim, in the Computing Office, Survey of India, and are available for reference.