In my last letter, of March, 1859, I told you about two active volcanoes that I discovered in the Gulf of Siam, one in the little isle of Koman, lat. 12° 30′ 29″ N., and long. 101° 50′ 2″ W., mer. of Greenwich, and of the probable existence of others whose workings were latent and slow. Since then I have travelled through Cambodia, from north to south and from east to west, gone up the Mekon as far as the frontier of Laos, visited one of the savage tribes which live between these two countries and Cochin China, then crossed the great lake Touli Sap, explored the provinces of Ongcor and Battambong, which are full of splendid ruins, one of which in particular, the temple of Ongcor, is almost perfect, and, perhaps, unequalled in the world. I then passed from the Mekon to the Menam, and returned to Bangkok. A low table-land, of which the gradual slope takes a week to ascend, separates the two rivers. A chain of mountains, of which the highest peak is 6274 English feet above the level of the sea, extends to the S.W., joins the ranges of Chantaboun, Pursak, and Thung Yai, which are from 4000 to 5000 feet high, and reaches nearly to Komput and Hatienne; while to the north another small chain, joining the greater one of Korat, runs eastward, throws some ramifications into the provinces of Battambong and Ongcor Borege, which is 40 miles farther north, and bears the name of the mountains of Somrai. Not being in direct communication with the Archæological Society, I wish to call your attention to the marvellous remains at Ongcor of the civilization of a great people. The country is rich in woods and mines, and although thinly populated, produces enough cotton for the use of Cochin China, while the great lake, which abounds in fish, furnishes an immense quantity of this article also to China. Iron of a superior quality is also abundant, and the Kouis, an ancient tribe of a primitive race, living east of the Mekon, who speak the same language as the Stiêns, work it very industriously. There are also many other mines, rich in gold, lead, and copper, in the chains to the east and west; that of Pursak produces the beautiful cardamom, which, when transplanted, gives fine stems but no fruit. Unluckily most of these mountains are frightfully unhealthy, and no one but those who have lived there from infancy can remain long among them with impunity. In the island of Phu-Quor or Koh Trou, which belongs to Cochin China, and which is very near to Komput, there are rich mines of cannel coal. I was not able to get there, the war having rendered the people hostile and cruel to all white men; but my attention having been drawn to it by some ornaments worked in this mineral by the islanders, I procured two specimens, which I send you.