The United States of America As Represented by the Secretary of

Stephan C Schroeder

Julius Frankel

Agostino Abbate

A system which enables the user to measure continuously or intermittently or by remote command the thickness changes, above or below the water, under variable temperature changes of underground culverts with reliability. A liquid delay is used to couple the sound to the culvert comprising a focused transducer (10) screwed into a hollow cone-like structure called a 'squirter' or 'bubbler' (11) providing the operator of the system a means for searching for good echoes from which calculations of thickness with a computer can be made using the known velocity and echo return times.

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Schenectady, NY, United States of America

Stephan C Schroeder