The computation of tabular quantities

Abstract

There is one phase of magnetic work which, although only of secondary importance as compared with its theoretical problems, is nevertheless of real practical importance to those who have in hand the preparation and publication of the results of magnetic observatory observations. It may be of interest to describe some of the methods which have recently been found effective in facilitating the preparation of the magnetic observatory results for the five observatories of the Coast and Geodetic Survey. Reference will be made only to the computation of the hourly values of the magnetic elements and to the diurnal variation tables.The hourly values of declination, horizontal and vertical intensities are, of course, computed by simply adding the converted hourly magnetogram scalings to constant base‐line values and applying corrections for temperature when necessary. There are several ways in which this may be done, depending largely on the facilities at hand and on the preferences of individual computers. The system to be described here includes the use of an addition table and a special copyholder, and these, when used in conjunction with a touch system adding and tabulating machine, enable computers with even very limited experience to attain a high degree of speed and accuracy. When it is realized that as many as three or four thousand tabular quantities might be computed in the course of a day, the reason for great attention to detail becomes very evident.