Skiff outfitted for hydrography - casting the lead. Skiff off of HYDROGRAPHER

Boston Whaler outfitted for hydrography. Boat off of PEIRCE

Small boat hydro - Cook Inlet area. Boat off of PATHFINDER

Low tide - rock shows where vessel struck and then sank. Vessel captain claimed to be in mid-channel far from any hazards. Paint, metal fragments, and rivets proved differently

Egyptian tomb painting from 1450 B.C. showing officer with sounding pole. Officer is telling crew to come ahead slow. Engineers with cat-o'-nine-tails assuring proper response from engines

St. Brendan striking out into the Atlantic - about 6th Century A.D. St. Brendan checking depths with his sounding pole

Frontispiece from the Hastings Rutter - 1450 A.D. early English pilot guide. Possibly first picture of leadline sounding

Sailor sounding from merchantman - Nineteenth Century. Sketch by Gordon Grant

Double sounding chair arrangement. Effort to double density of soundings. Working off of HYDROGRAPHER in 20 to 25 fathoms

Double sounding chair arrangement. Effort to double density of soundings. Working off of HYDROGRAPHER in 20 to 25 fathoms

Double sounding chair arrangement. Effort to double density of soundings. Working off of HYDROGRAPHER in 20 to 25 fathoms

Taking the reading when the line is vertical

Boatswain Jahnke casting the lead. Launch off the SURVEYOR

Casting the lead - Hydro Manual 1931

Casting the lead - Hydro Manual 1931

Leadline is vertical for reading. Working off the WESTDAHL

Tossing the leadline. Working off the WESTDAHL. Note splash of lead out ahead of ship

Sounding in Salton Sea for seaplane landing site. Part of war project to establish seaplane landing sites. Sites used for ferrying seaplanes across United States

Trolley sounding arrangement. Off of ISIS

Trolley and line ready for next sounding. Off of ISIS

Trolley rig - Hauling slack from sounding line prior to sounding. Off of ISIS

Trolley rig - paying out leadline by hand as trolley carriage runs down cable. Off of ISIS

Getting upright cast as sounding stand passes position of lead. Off of ISIS

Hauling in sounding line of trolley rig using hand crank on boat deck. Off of ISIS

Arrangement of sounding machines on PATHFINDER. Off of PATHFINDER

Arrangement of sounding machines on PATHFINDER. Off of PATHFINDER

Arrangement of sounding machine on PIONEER. Off of PIONEER

Coast and Geodetic Survey sounding tube equipment. Hydrographic Manual 1931, Figure 17, p. 53

Shelter and equipment used in reading sounding tubes. Off of PIONEER

Robert Williams with first Fessenden oscillator on the tug Susie D. First successful test of sonic system. Looking for icebergs but also found bottom

Sonic sounding apparatus on the GUIDE. On the ship GUIDE

Title page to manual - "The Submarine Fathometer". Fathometer invented by Herbert Grove Dorsey of the Sub Signal Corporation.

Fathometer Filter. From the manual - "The Submarine Fathometer"

Fathometer Oscillator. From the manual - "The Submarine Fathometer"

Internal View of Fathometer. From the manual - "The Submarine Fathometer"

Herbert Grove Dorsey - chief physicist of the Coast and Geodetic Survey. With Dorsey Fathometer - Dorsey came to work with C&GS in 1926

Operator using Dorsey Fathometer with flashing light method. Merchant Marine Bulletin No. 9, May 1931

Leo Otis Colbert with Dorsey Fathometer No. 3. The first effective shallow and deep water echosounder. Operator watched flashing light. On the ship OCEANOGRAPHER

808 fathometer transducer. Hydrographic Manual 1942. Called first portable sonic sounding device. First acoustic sounding device used on C&GS sounding boats for shallow water. First use of shallow water fathometer continuous records by C&GS

Prototype "portable" depth recorder used as part of 808 fathometer system. Bulletin 13 of the Association of Field Engineers, 1939, p. 102

"Echometre" record from S. S. De Grasse. Crossing over canyon near Georges Bank. Bulletin 4 of the Association of Field Engineers, Dec. 1931, p. 83

Early graphic record from Sub Signal system. Off S.S. Yarmouth between Boston and Yarmouth. Bulletin 6 of the Association of Field Engineers, Dec. 1932, p. 60.

Various bottom configurations plus bar check record. Hydrographic Manual 1942

Various bottom configurations. Hydrographic Manual 1942

Ship on Nantucket Shoals that was subsequently blown up. Fathometer record of remains of ship

Expanded view of fathometer record of remains of ship

Outer Nushagak Bay sand waves. Observed on PATHFINDER

Hydrothermal spring discharging fluid off Pagan Island. Observed on NOAA Ship TOWNSEND CROMWELL

Running up to bank and loosing trace - then heading back out into bay. Record from PEIRCE launch in Delaware Bay 1985

Ragged appearing fathogram trace caused by coral heads. Record from PEIRCE launch off Eleuthera Island