Ritchie-Haskell direction current meter as used on the U.S. Fish Commission steamer FISH HAWK.

Towing a Roberts Radio Current Meter buoy to its planned station site from the USC&GS Ship MARMER.

Graphical output from the first operationally deployed Roberts Radio Current Meter.

Deploying mechnaical current meter from hand-operated winch.

Self-registering tide gauge

Graphical record of tidal currents at the entrance to San Francisco Bay.

Graphical records of tides in different tidal regime areas on the coastline of the United States.

Graphical record of tides with superimposed disturbance. This record was obtained a week prior to the Long Beach Earthquake of March 10 so it was not related to that major seismic event.

The strike clock for old style automatic tide gauge. By D. L. Parkhurst.

Preparing a Roberts Radio Current Meter buoy for deployment off the USC&GS Ship EXPLORER.

Tidal current curve, San Francisco Light Vessel. The time, direction, and magnitude of the current is referred to the times of predicted tide at the San Francisco, Fort Point.

Clock and tide indicator in public viewing area of a Coast and Geodetic Survey tide house.

Tide indicator mechanism of the tide indicator at the Maritime Exchange at Philadelphia.

Tide indicator display indicating rising water level.

Tide indicator display indicating slack water.

Tide indicator at Fort Hamilton. The pointer moves around the dial indicating the height of tides referred to mean low water. The arrow points upward when the tide is rising and downward when the tide is falling. The indicator is showing slack water at high tide in this image.

Reedy Island, Delaware River, pier and tidal indicator by moonlight. The indicator tells the mariner that the tide is falling.

Reedy Island, Delaware River, pier and tidal indicator. The indicator tells the mariner that the tide is falling.

Back side of the Reedy Island tide indicator.

Constructing the tide indicator at Alcatraz Island.

Scaffolding for painting numerals and unit indicators on tide indicator. Right hand: Clear numerals on tide indicator after painting. Tide indicator points up , showing a rising tide.

Woman professional operating the USC&GS tide prediction machine during World War II.

The USC&GS tide prediction machine No. 2, enclosed in wood casing. This computing machine is still fondly referred to as "Old Brass Brains."

Changing constituent elements for computing tides for a different location on USC&GS tide prediction machine No. 2.

Mr. Disney of the Tides and Currents Division instructing trainee from the Philippine Coast and Geodetic Survey on the operation of tide-prediction machine no. 2, "Old Brass Brains."

Recording tide predictions from the dials of the U.S. Coast and Geodetic Survey tide-predicting machine. The operator is Burt W. Wilcox.

Front indicator panel showing traced tide curve and various dials related to predicting tide with Tide Prediction machine No. 2, "Old Brass Brains."

Adjusting various constituent gears for predicting tide at a specific location on the surface of the earth. Tide-prediction machine No. 2, "Old Brass Brains."

Adjusting various constituent gears for predicting tide at a specific location on the surface of the earth. Tide-prediction machine No. 2, "Old Brass Brains."

The interior of the Coast and Geodetic Survey tide-prediction machine designed and built by Dr. Rollin Harris and Chief Instrument Maker Ernst G. Fisher.

Coast Survey employee Susan Tully using new automated tabulating machine for recording tides predicted on Tide Prediction Machine No. 2, the Fisher-Harris machine. With the advent of electronic computers in the 1960's, this venerable machine became obsolete and is now located in the NOAA Science Center in Silver Spring. It is known as "Old Brass Brains."

View of back side of tide-prediction machine No. 1, the Ferrel tide-prediction machine.

Side view of tide-prediction machine No. 1, the Ferrel tide-prediction machine.

Current observation from deck of U.S.S. BACHE in Norfolk Harbor.

Shoal sand ridges on Georges Bank causing surface disturbance

Shoal sand ridges on Georges Bank causing surface disturbance

Chart of the Gulf Stream produced in 1854 from systematic Coast Survey observations beginning in 1845.

Woodcut of tidal bore on the Seine River at Caudebec. In: Flammarion, G. 1890? "Popular Astronomy," English Translation. P. 170. D. Appleton and Company, New York.

Fishing at Dutch Harbor during an inport.

On the working grounds, a survey launch is dwarfed by the volcanic shores of the Aleutian Islands.

Servicing a tide gauge

Horizontal control work in the Aleutian Islands

Observing angles with a theodolite on a chilly day in the Aleutian Islands.

Tending a tide gage.

Cartoon showing pigs running from the tidal bore in an arm of the Bay of Fundy. The pigs would run out when the tide receded and catch stranded fish and shellfish while one of their number would stay on a high point and warn of the approaching bore.

Leveling a Nation. Leveling operations at Point Loma Lighthouse, the southwestern corner of the contiguous United States.

Leveling crew working somewhere on West Coast. Party chief with hat on and standing by instrument. Instrument mounted on railroad motorized speeder. Party chief is Lt. C. A. Egner.

Level crew using motorized speeders on railroad.

Configuration of speeder used in leveling operations along railroad.

Rodman maintaining rod in vertical position over mark while steam engine approaches. Speeder crew moving speeder off track close to steam engine.