There are several extinct volcanoes in Pechaburi, four of which I have ascertained to form part of the numerous detached and conical hills which are probably all ancient craters belonging to the great chain Khao Deng, which occupies all the northern part of the centre of the Malayan peninsula, and is inhabited by the Kariens, a primitive and independent people, who, like the Stiêns and other tribes, have doubtless been driven back to the mountains by the encroachments of the Siamese, and where the inclemency of the climate protects them against all attacks from their neighbours. The mountains are known in the country as the Na-Khou, Khao, Panom Knot, Khao Tamonne, and Khao Samroum. The last two are 1700 and 1900 feet above the level of the sea, and only a few leagues distant from each other. All these craters appear to have been originally upheaved (“craters of elevation” M. de Buch styles them) from the bottom of the water, at a period when all this part of the country, as far as the great chain, which I have not yet been able to visit, was under the sea. Besides an immense volcanic cone, in part fallen in, and where the ground resounds under one’s feet, each of the mounts has several lateral mouths and a number of fissures and chimneys, or passages, which bear evident traces of subterranean fires. They are entirely composed of trachytic rocks, scoria, lava, felspar, &c. The Siamese have made temples of the largest of these caverns, which are of great depth and breadth, and extremely picturesque. One of the caverns of Samroum is quite inaccessible. Having descended to the depth of 20 feet by a chimney 2 feet wide at its mouth, and shut in between rocks, I found myself at the entrance of a deep cavern, but there all my efforts to proceed farther were defeated; a few steps from the entrance my torch suddenly went out, my breathing was checked, and I in vain fired my gun several times in order to disperse the foul air. TO M. CHARLES MOUHOT (HIS BROTHER). Bangkok, 13th October, 1860. To you, my dear brother, I address my last letter before quitting Bangkok for my long journey to Laos. I have waited till the last moment for the steamer which ought to bring me letters from Europe, but unfortunately I am obliged to set out without receiving any answers to those which I sent in May, on my return from Cambodia. I fear that, once in the interior of the country, I shall have no means of sending letters; arm yourself, therefore, with patience, dear brother, and do not think me neglectful if you do not receive any; but be sure that I, alone in those profound solitudes, shall suffer more than you, from my ignorance of everything concerning those dear to me; and during the eighteen or twenty months which the journey will probably occupy I shall not see a European face nor hear a word which can recall to me my beloved country.