THE new number of the Izvestia of the Russian Geographical Society contains the long-expected letters from Col. Prshevalsky on his adventurous journey on the frontier of Tibet. We have already referred to Col. Prshevalsky's work; the following further details will be of interest:—His last news were dated from Hami, whence he proposed to go south-east to Tsaïdam. But it, was impossible to find a guide: a Chinese, given for this purpose by the Hami authorities, left the expedition some fifty miles from the town, after having led the travellers into a region full of great ravines. M. Prshevalsky, confident in his eleven companions, resolved to find his way himself by sending every day two men on horseback for distances of thirty and fifty miles round to discover the best direction. The advance was very slow, and the travellers spent one month and a half in the mountains south of Sa-djeou, discovering the high mountain-ranges to which they gave the names of Humboldt and Ritter. After a march of 190 miles they arrived at Kourlyk in the Tsaïdam, but here also they were badly received, and could not find guides, owing to the secret influence of the Chinese. Finally M. Prshevalsky told the chief of Kourlyk that he would take him as guide to Tibet if another guide could not be found, and on the following day the guide was found.