Digital Library Search
Image
Download ( 1.43 MB )Permalink
https://www.noaa.gov/media/digital-library-photo/pl23ship4043jpgDescription
Figure 38. Percussion current meter invented by Julien Thoulet. Top: Number99 0610. Bottom: Number 99 0611. When the helix turned it caused a striker to fall on a steel plate. The sound of this was recorded by a hydrophone and thenumber of recorded sounds per unit time was directly related to current strength. This was tested off Monaco by Dr. Jules Richard in 1921. (Image credit: Oceanographic Museum of Monaco | P. Roggero)