Noteworthy advances have been made in geophysical apparatus for oil prospecting purposes over the past twelve years. Highly sensitive apparatus for accurate registration in an aeroplane of anomalies in the earth's magnetic field is being employed with considerable success. Gravimeters weighing only 5 lb and measuring changes in the earth's gravitational field with an accuracy of the order of 1 × 10^-8 g are in widespread use. Highly portable low frequency seismic apparatus will register with ease refracted waves up to distances of twenty miles, and seismic reflexion equipment of complex design, but rugged and portable, will record reflexions of various frequencies from depths of many thousands of feet. Routine seismic surveys are conducted from ships over water-covered areas, and for accurate location purposes on surveys over prospects under the sea it is customary to employ radio surveying aids. The recent introduction of magnetic recording for seismic surveys offers wide scope for improvements in the seismic technique; and new methods of displaying the recorded information are likely to help greatly the process of interpretation. Remarkable ingenuity has been shown in the development of radioactive and other forms of well-logging devices.