Historical Question, Possible Wade-Giles, Sichuan river name
Tung river is the translation of 銅河, it's called 大渡河 (Dadu river) now.

On page 127 of the "to the snows of tibet through china", it was written:


  . . . Lu-ting-chiao, which is built on both banks of the Tung River, . . .


Well, Lu-ting-chiao is 瀘定橋.

BTW, there's a map on page 353, you may compare it with other source :)

Another interesting book about tibet, thanks :)