Definition of "Tan"

The Tae ping camps commanded the Tan river which, flowing eastward, becomes further on the Wei, under which name it joins the Grand Canal at Lin tsing, on the northern side of the highest level of the Canal waters.

1856, Thomas Taylor Meadows, “Military History of the Tae pings, After the Occupation of Nanking, Up to the Present Time”, in The Chinese and their Rebellions‎, London: Smith, Elder & Co., page 175

As regards other possible railways in Shensi and Kansu not yet definitely projected, the most attractive is a line from the neighbourhood of Chingtzu Kuan in south-western Honan up the Tan River valley and across the Ch'inling Shan to Hsian.

1921, Eric Teichman, Travels of a Consular Officer in North-West China‎, Cambridge University Press, page 214

I was much disappointed at learning that the water was too low for navigation on the Tan river as yet, and that we would have to travel four days over the mountains to Kingtzekuan, on the border of Honan, before we should find the river navigable.

1923, Frits Holm, My Nestorian Adventure in China‎, Fleming H. Revell Company, page 191

In mid-March 1914 the White Wolf band gathered with a number of other rural bands at Ching-tzu-kuan, a cluster of houses at a pass on the Tan river at the Honan-Shensi provincial borders.[...]They continued through the Tsinling mountains above the Tan river valley on a high trad under yet higher caves where villagers traditionally hide.

1974, Edward Friedman, Backward Toward Revolution: the Chinese Revolutionary Party‎, University of California Press, published 1977, pages 152–153