X. A determination of the value of the earth's magnetic field in international units, and a comparison of the results with the values given by the Kew observatory standard instruments

The discrepancies found by Professor Rücker and the author to exist between the values for the horizontal component of the earth’s magnetic field, as measured by the absolute instruments in use in the various British observatories, were so great that it seemed of interest to measure the field at one of the observatories by an entirely different method, in order, if possible, to obtain some indication as to the reliability of the various instruments. Further, in the ordinary method of measuring H, a correction has to be applied on account of the distribution of the magnetism in the magnets employed, about the value of which there is some uncertainty.