Inland Waterways Association Waterways: T (note: the tidal river is generally regarded as navigable from Plymouth Sound to Weir Head, a length of 19.0 miles.)
The three present-day 'exceptions' can be clearly seen on the Tamar catchment map (on WikiCommons).
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Barton, Denys (1964). A Historical Survey of Mines and Mineral Railways of East Cornwall and West Devon. Truro: Bradford Barton. pp. 99, 101. OCLC12216380.