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Inserting smoke-glass slide into slide-holder for use in bathythermograph.

Inserting smoke-glass slide into slide-holder for use in bathythermograph.
Inserting smoke-glass slide into slide-holder for use in bathythermograph.
Inserting smoke-glass slide into slide-holder for use in bathythermograph.
Inserting smoke-glass slide into slide-holder for use in bathythermograph.
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Inserting smoke-glass slide into slide-holder for use in bathythermograph.
Still Image
12/14/1940
com/cullen/BT Slide.jpg
Date is approximate.
Image Of the Day caption:
Early in the twentieth century, oceanographers used a device called a bathythermograph (BT) to record water temperature beneath the surface on glass slides coated with smoke and oil to. Invented in the late 1930's, the re-usable probes preserved information that proved critical to the U.S. Navy's growing fleet of submarines and anti-submarine activities. As the metal BT dropped through the water, a bellows contracted under the increasing pressure, moving the attached slide along one axis. Another component changed shape as temperature changed, moving a stylus that scratched a line in the coating. The resulting plots could then be interpreted with gridded readers, as in this 1940 photo.
Caption from Down to the Sea for Science, pg. 58:
A compressible bellows within the BT was coupled with a stylus resting on a smoked-glass slide coated with a mixture of smoke and oil. When the stylus moved in response to temperature changes and the slide responded to depth changes, a record was scratched in the smoke. After retrieving the BT and removing the slide, the watch stander scratched the cruise and slide numbers as well as the latitude, longitude, and time into the coating and fixed it with a dip into lacquer. During World War II, thousands of these slides were forwarded monthly to processing centers. In this photo from a BT instruction manual, a data processor has inserted a slide into a holder that supplies the temperature grid.
Photo courtesy of WHOI Archives, ©Woods Hole Oceanographic Institution
© Woods Hole Oceanographic Institution
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