Beginnings: Challenger Sounding Station 272

Nov 21, 2022 

By Philip Pearson

It’s a remarkable story, really. On 8 September 1875, Challenger reached a point in the middle of the Pacific Ocean, Sounding Station number 272, where the scientists and crew began another day’s work. Here, they lowered their equipment into the sea to record the ocean’s depth (2,600 fathoms, or 15,600 feet), trawl the sea floor for marine specimens, and test the water temperature and salinity. Their findings were unique enough at the time. But today, 150 years later, their simple but pioneering, hand-made measurements have become benchmarks to study changes to marine life, ocean acidity and ocean temperatures, driven by climate change and man-made carbon emissions since the industrial revolution.

To gather samples that day in 1875, the crew lowered a cable nearly three miles long to the sea floor. Weights, sampling bottles, thermometers and a trawling bag were attached to the line, with coloured flags at intervals to count out the length of line the crew paid out.

Sounding Station 272, mid-Pacific Ocean, one of Challenger’s 354 sounding points.

Source: Nature magazine, 2020.

If there was a sea breeze, the steam engine held the ship steady, head to wind:

A workable and more reliable dredging routine was soon established. Steam power was an essential part of the operation. ‘The first thing to be done,’ writes engineer Spry, ‘is to shorten and furl all sail and bring the ship head to wind, regulating her engine speed in such a manner as to avoid forcing her through water.’ With the ship held steady in position at the sounding station, the screw turning slowly, work could then begin.


Sub-Lieutenant Swire led the sounding operations designed to measure the depth and other conditions of the oceans. The sailors assembled the inch-thick depth-sounding lines, stacking them on deck in reels 3000-fathoms long (about three and a half miles).


Source: A Challenger’s Song, page 123

Dredging and Sounding arrangements on board the Challenger

Scientists at work aboard ship. Challenger Report