In response to the need for a more accurate method of measuring the vertical magnetic intensity in the field, voiced to me in 1938 by Captain N. H. Heck, of the United States Coast and Geodetic Survey, the Gulf Research and Development Company built an absolute magnetometer of new design for the determination of declination (D), vertical intensity (Z), and horizontal intensity (H). The declination is measured in the customary manner by means of a fiber‐suspended magnet. The intensity‐measurements are made by comparing the field of a Helmholtz coil with the component of the Earth's field that is to be measured. H is obtained by the sine‐galvanometer method. The zero‐field detecting device for Z is a special vertical field‐balance in which the polarity of the magnet can be reversed by discharging a condenser through magnetizing coils fastened to the case. The effect of residual mechanical unbalance is thus made to disappear from the average of two sets of observations taken with the magnet oppositely polarized, The Helmholtz coil‐constant for the Z‐magnet is determined by suspending the Z‐magnet in the sine‐galvanometer housing, and comparing the value of H so obtained with an observatory base‐line.From preliminary tests at Cheltenham in April, 1940, the declination‐error was 1.′6. The precision of the intensity‐measurements is limited entirely by the stability of electrical standards in the field. This is estimated to be between 0.01 and 0.02 per cent. Six standard cells, two standard resistors, and one Rubicon potentiometer comprise the electrical measuring‐equipment. The determination of Z on the basis of the Cheltenham base‐line for H and the electrical equipment of the CIW sine‐galvanometer No. 1 was 17γ greater than the Cheltenham base‐line for Z. This discrepancy can be accounted for either by pier‐differences or by a magnetic impurity in the construction of the Z‐balance. The tests were interrupted by the war. Since little remains to be done to the instrument, it is hoped that it will be made ready for the postwar observational program at an early date.