It remains to consider the measurement of the declination and the horizontal component, these two elements being generally measured with the same instrument, which is called a unifilar magnetometer.
- Unifilar Magnetometer, arranged to indicate declination.
The Kew Observatory pattern unifilar magnetometer is shown in figs.
In the case of the Kew pattern unifilar the same magnet that is used for the declination is usually employed for determining H, and for the purposes of the vibration experiment it is mounted as for the observation of the magnetic meridian.
- Unifilar Magnetometer, arranged to show deflexion.