ou a cru démontrer qu'un lac à bassin fermé ne pouvait avoir les eaux douces, mais nous avons rencontré au Tibet des lacs à bassin fermé dont l'eau est douce et tous les indigènes que j'ai consultés ont été d'accord pour affirmer que les eaux du Lob nor sont salées, sauf sur le chenal du Tarim. Quant à l'argument tiré de ce que Marco Polo ne parle point du Lob nor, je m'étonne qu'il ait été émis: Marco Polo qui est toujours très bref ne cite pas à beaucoup près tout ce qu'il a vu ni tout ce dont il a ouï parler et il ne prévoyait pas que les savants futurs se querelleraient à propos d'un lac qui pour lui n'était qu'un marais insignifiant. La tradition indigène est trop ferme et trop précise pour que l'on se risque à placer le Lob nor autre part qu'elle ne le met.»*
Confining myself to one or two observations upon this passage. The self-contained lakes, with fresh water, which Grenard visited in Tibet will certainly have a subterranean outlet, and their isolation is only apparent. I have myself seen several lakes of this character in Tibet. A lake that occupies the lowest depression in a basin, and possesses neither visible nor invisible outlet, must of necessity become salt. It is for this reason that the water of the Kara-koschun turns salt, and its salinity will continue to increase as the years go on. Marco Polo's omission to describe, or even mention, the Lop-nor is now a matter of no consequence. All the same, if he had heard anything about the existence of an extensive lake, with inhabited shores, in the middle of the desert, I do not believe he would have said, that it takes a whole year to cross the Desert of Lop. It is true, that in most cases local tradition is very reliable; yet to this credibility there exists a limit, and that limit does not extend beyond many generations backwards. This applies with especial force in the case of a lake which has had for successive masters, first the Chinese, then the Mongols, and finally the Turks. Of the earlier phases of its history the last-named possess not the slightest inkling.
If then Grenard has not made any noteworthy contribution to the solution of the Lop-nor problem — as that problem stood in 1898 — what he says upon the question is of great interest, albeit, now that the question is definitively solved, it is the interest of curiosity only.
Finally I may add that Mr. Henri Cordier has given a most interesting and valuable resumé of the Lop-nor problem in his new edition of Yule's Marco Polo. Cordier is quite right when he expresses his own opinion in the following words: »There is no doubt as to the discovery of Prjevalsky's Lob-nor, but this does not appear to be the old Chinese Lob-nor; in fact, there may have been several lakes co-existent; probably there was one to the east of the mass of water described by Dr. Sven Hedin, near the old route from Korla to Shachau; there is no fixity in these waterspreads and the soil of this part of Asia, and in the course of few years some discrepancies will naturally arise between the observations of different travellers.» Although this passage was written before my last journey, it perfectly agrees with my new discoveries in the Lop-nor region**
* F. Grenard (J.-L. Dutreuil de Rhins), »Mission Scient17ue dans la Haute Asie, 189o-1895», Vol. III. pp. 192 ff.
*0 The Book of Ser Marco Polo, Vol. I, p. 198 ff.
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