Compass rose for use by mariners in comparing magnetic direction with true direction.

Magnetogram plots.

Magnetogram plots.

United States repeating stations as of 1969

Edmund Halley's isogonic chart of 1701 showing lines of equal magnetic declination. This was the earliest chart of this nature and one of the earliest geophysical thematic maps.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveying operations associated with determination of magnetic declination.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Observer operating field-type Ruska magnetometer.

Observer operating field-type Ruska magnetometer.

Calibrating geomagnetic instruments at the Coast and Geodetic Survey geomagnetic observatory at Corbin, Virginia.

Calibrating geomagnetic instruments at the Coast and Geodetic Survey geomagnetic observatory at Corbin, Virginia.

Administrative Building at Fredericksburg Geomagnetic Observatory

Honolulu Geophysical Observatory

Honolulu Geophysical Observatory

Honolulu Geophysical Observatory. The vault?

Honolulu Geophysical Observatory

College, Alaska, seismic and magnetic observatory

College, Alaska, magnetic observatory

Quartz horizontal magnetometer

Quartz horizontal magnetometer

Universal gravitometer (synonymous with gravity meter - not in the sense of an instrument to measure specific gravity)

Universal gravitometer (synonymous with gravity meter - not in the sense of an instrument to measure specific gravity)

A seismograph record of the Long Beach Earthquake of March 10, 1933.

A strong-motion accelerograph, an instrument used to measure the accelerations due to earthquake waves shaking the ground or structures. The accompanying record was of the Helena, Montana earthquake of October 31, 1935. In: Bulletin of the Geological Society of America, Vol. 49., No. 1, pp. 1-21.

Overhead view of a Coast and Geodetic Survey strong-motion accelerograph.

A vibration meter for recording building and ground vibrations.

Earthquake epicenters off the West Coast of the United States and Mexico as observed through early 1927.

Earthquake epicenters in the Western and Northern Pacific Ocean as of early 1927

"Earthquake Zones", world seismicity map clearly showing the correlation of the Pacific Ring of Fire with earthquake epicenters, the Alpine-Himalayan Belt, and the coincidence of major portions of the mid-ocean ridge system with areas of seismicity. Map published in The Geographical Review, Vol. XXV, No. 1, 1935, Pl. 1.

The correlation of high seismicity with the Mid-Atlantic Ridge. This map was produced in 1937. Note the refinement of earthquake zones on this map as compared to the map in image cgs02174. In: Proceedings of the American Philosophical Society, Vol. 79, No. 1, Symposium on the Exploration of the Ocean Bottom Arranged by the American Geophysical Union (April 21, 1938), pp. 97-108.

The correlation of high seismicity with what is now known as the Gakkel Ridge, a segment of the mid-ocean ridge system. In: Proceedings of the American Philosophical Society, Vol. 79, No. 1, Symposium on the Exploration of the Ocean Bottom Arranged by the American Geophysical Union (April 21, 1938), pp. 97-108. The first hint that the Mid-Atlantic Ridge continued through the Arctic Ocean.

A median section through the earth showing composition of the interior and transmission of earthquake waves. In: Earthquakes and Astronomy" by N. H. Heck. Published in: The Sky, March 1937. P. 14.

Newly uplifted seafloor along fault-line in SE Alaska. The beach was elevated 47 feet 4 inches on the west side of Disenchantment Bay. Yakutat Bay earthquake of September 1899.

Japanese fishing vessel thrown ashore by tsunami accompanying earthquake of March 7, 1933, on the Sanriku coast of Japan.

Title page of computation book of ' Triangles for the Survey of the Coast' made in 1817 by F.R. Hassler.

Field sketch of triangulation stations- ' North-Eastern view from Buttermilk Hill.'

Field sketch of New York City as seen from Staten Island. ' North East view of the Horizon as seen from the fire Signal on Staten Island.'

View from triangulation station Fort Hale.

Westerly view from triangulation station Stony Hill. View includes conical tin signal on pole for seeing reflected sun at great distance.

Westerly view from triangulation station West Rock near New Haven.

Two telescopic views. Top view is of Osborne Hill as seen from Mt. Carmel. Bottom view is of Harrow Hill signal as seen from Buttermilk Hill.

Two telescopic views. Friar's Head Signal as seen from Mt. Carmel. Ruland Hill Signal as seen from Mt. Carmel.

Two telescopic views. Hempstead Harbor Signal as seen from Bald Hill. Loaf Hill Signal as seen from Bald Hill.

Ruland Hill Signal as seen from Mt. Carmel.

Friars Head signal as seen from Mt.Carmel.

Loaf Hill signal as seen from Bald Hill.

Finished view from Mt.Carmel looking to North East No.1