NOTE 1.—_Ḳará-Muren_, or Black River, is one of the names applied by the Mongols to the Hwang Ho, or Yellow River, of the Chinese, and is used by all the mediæval western writers, _e.g._ Odoric, John Marignolli, Rashiduddin. The River, where it skirts Shan-si, is for the most part difficult both of access and of passage, and ill adapted to navigation, owing to the violence of the stream. Whatever there is of navigation is confined to the transport of coal down-stream from Western Shan-si, in large flats. Mr. Elias, who has noted the River’s level by aneroid at two points 920 miles apart, calculated the fall over that distance, which includes the contour of Shan-si, at 4 feet per mile. The best part for navigation is above this, from Ning-hia to Chaghan Kuren (in about 110° E. long.), in which Captain Prjevalski’s observations give a fall of less than 6 inches per mile. (_Richthofen_, _Letter_ VII. 25; _Williamson_, I. 69; _J. R. G. S._ XLIII. p. 115; _Petermann_, 1873, pp. 89–91.) [On 5th January, 1889, Mr. Rockhill coming to the Yellow River from P’ing-yang, found (_Land of the Lamas_, p. 17) that “the river was between 500 and 600 yards wide, a sluggish, muddy stream, then covered with floating ice about a foot thick.... The Yellow River here is shallow, in the main channel only is it four or five feet deep.” The Rev. C. Holcombe, who crossed in October, says (p. 65): that “it was nowhere more than 6 feet deep, and on returning, three of the boatmen sprang into the water in midstream and waded ashore, carrying a line from the ferry-boat to prevent us from rapidly drifting down with the current. The water was just up to their hips.”—H. C.] NOTE 2.—It is remarkable that the abundance of silk in Shan-si and Shen-si is so distinctly mentioned in these chapters, whereas now there is next to no silk at all grown in these districts. Is this the result of a change of climate, or only a commercial change? Baron Richthofen, to whom I have referred the question, believes it to be due to the former cause: “No tract in China would appear to have suffered so much by a change of climate as Shen-si and Southern Shan-si.” [See pp. 11–12.] NOTE 3.—The _asper_ or _akché_ (both meaning “white”) of the Mongols at Tana or Azov I have elsewhere calculated, from Pegolotti’s data (_Cathay_, p. 298), to have contained about 0_s._ 2·8_d._ worth of silver, which is _less_ than the grosso; but the name may have had a loose application to small silver coins in other countries of Asia. Possibly the money intended may have been the 50 _tsien_ note. (See note 1, ch. xxiv. _supra_.) CHAPTER XLI. CONCERNING THE CITY OF KENJANFU.